Romania vs. Czech Republic vs. Belgium vs. Croatia

I would probably rule out Croatia because a lot of the beauty is the islands and coastline, and the timeframe you're contemplating isn't ideal. I would pick some combination of larger cities with a good mix of indoor activities in case weather isn't great.

Yeah, my brain immediately turns to the weather. I suggest using timeanddate.com to take a look at the actual, day-by-day historical weather statistics for February/March of several recent years. I haven't done that, because I know what my reaction would be. I leave it to you to decide what works for you. For rainfall/days with rain I find the summary charts on the cities' Wikipedia pages to be all I need; I just don't consider average monthly high and low temperatures adequate for revealing how grim it might get.

Prague and Dresden both have a lot of museums and for me nine days wouldn't be too long, weather aside. Berlin and Dresden would be another good combination; Berlin has tons of indoor sights and not as much pretty architecture as Prague.

I assume Brussels also has good museums, though I have never been to Belgium. Most folks here are not very fond of Brussels. Some of them would probably suggest that you combine Bruges with Ghent or Antwerp. Nine days is sort of a long time...

Zagreb is a museum-rich city, but I agree with Agnes about visiting Croatia at a better time of year--which would be any other time of year. (But I'd say that about anywhere in Europe with the possible exception of places like Andalucia, Sicily, etc.) I had a miserably chilly, wet day in Zagreb in the first half of October 2015. Ljubljana doesn't have as many indoor sights as Zagreb but is a charming place--as long as the weather isn't miserable. Most people who go to Slovenia like to see some of the rural areas, which means being outdoors. I don't think of Ljubljana as a place to hunker down in the winter for a long visit.

Bucharest was not in my Top 5 Romanian destinations. It has only scattered historic architecture remaining, thanks to Ceausescu. There will be museums (I visited none), but if you want to see Old World Romania, you'll probably have to hoof it a lot, which might not be a lot of fun in February/March. The cities I liked better were Timisoara, Cluj-Napoca, Sibiu, Brasov an Sighisoara. Romania is a somewhat challenging country to visit, because the ground transportation is so slow. Nine days is certainly not too long for Romania, but I wouldn't go there in the winter. Be sure to read a bunch of hotel reviews to be sure the heating is adequate. Construction standards were very low in Romania during the Ceausescu years, and many buildings are poorly insulated, if at all.

If I had to travel in the winter and choose from among your options, I think I'd go for Prague + Dresden.

@luftmensch Thanks for your input. I like going to museums, history, and just walking around and admiring the architecture. I would be traveling by train

@James E. I went to Budapest a couple of years ago and I absolutely loved it! I'd love to go back but I'm torn between seeing a new place or going back to a place I've already been. When I was in Budapest it was around the same time of year, however the calendar didn't line up for Mohacs. I also had plans to drive tanks but the weather didn't cooperate and it was still pretty cold and the tank operator was closed. As far as your question, why Belgium? I haven't been there and think it could be fun. I don't know, I could be wrong. I want to see and explore different places. I've been to Paris and I missed out on Versalles and Normandy beaches. I think a trip to Belgium could be a good way to get to Paris and see what I missed last time.

@luftmensch Whoa! Thank you! I didn't even think to see if I could drive tanks somewhere else. Have you done any of these? I wasn't sure if adding Berlin would be feasible.

@James E. Thanks. I often travel around February and March and I don't think the weather makes or breaks a trip like some do. I'm not going to lounge on the beach. I'm going to explore. If it's cold or rainy so be it. Have you had any trouble with Wizzair? I really did love Budapest. The opera house was under renovation while I was there, so I only got to see part of it. I took one day and went to Vienna. I'd love to go back and do the same thing and add Bratislava to the mix.

@luftmensch Thanks for all your input. If you had 9 days to divide between Prague, Dresden, and Berlin, how many days would you spend in each place? And how many days would you spend in each place for a Belgium trip?

Maximum 2 nights in Dresden because there's so much more to see in Berlin and Prague. I spent six days seeing the sights in Berlin and didn't have time for the German History Museum. But few visitors would go to as many Cold War sights as I did.

When I had to rough out my time allocation in Ukraine two years ago, I compiled notes from guidebooks and this forum, then I listed the things I wanted to see in L'viv and Kyiv. The Kyiv list was twice as long the L'viv list (and it's a much larger city, so things are more spread out), so I planned twice as many days in Kyiv even though L'viv is the city everyone gushes about. That process worked well.

On average, Berlin's sights were, for me, individually more time-consuming than those in Prague. The museums are larger, there's more explanatory material to absorb at most of the historic sites, etc.
However, I ran out of time in the Museum of Communism (Prague) and had to return the next day.

Honestly, I'd drop Dresden if I were going to go to both Berlin and Prague in 9 days. I admit to being a slow traveler.

My sadly cancelled trip to Romania for May had the following itinerary:

SFO to Cluj-Napoca, stay 3 nights
bus to Sibiu, stay 3 nights
bus to Brasov, stay 3 nights - day trip to Sighisoara
bus to Bucharest, stay 2 nights
fly to Budapest for 4 nights before home

I chose to start in Cluj and work my way down to Bucharest as it was easier to get a short, direct, cheap flight from there to Budapest. Bucharest and Brasov would be 2 interesting and close enough to each other cities.

I also have Brussels and Bruges (also Ghent on the way) and a second visit to Paris on my list, perhaps 3 days Brussels, train and overnight or 2 in Ghent, train to Bruges for 4 nights (want to see WWI trenches as a day trip), then train to Paris for 4 days or so.

@luftmensch Thank you for your advice. I really appreciate it! Here's the link for driving tanks in Budapest http://tank.hu/index_en.php I'm definitely intrigued by the Carnival of Aalst. I've been to Carnival in Venice and Luzerne. I enjoyed both and would love to check it out

@James E. How many times have you been to Budapest? I'm leaning towards Prague/Belgium; Belgium; or Budapest. You're making me want to go back to Budapest so badly

@luftmensch What are your thoughts on Belgium? It appears many people do not like Belgium but I'm not sure why

@James E. I really did like Budapest. I wish I had more vacation time so I could go to Budapest for a week and Belgium or Prague for a week. You mentioned previously that you did not care for Prague. What are your thoughts on Belgium?

Regarding your previous question regarding thoughts on Belgium, this quote:

I like going to museums, history, and just walking around and admiring
the architecture

Heck, you'd do just fine in Belgium. I'll humbly admit that we've only seen pieces of it (Brussels, Bruges, Gent and Antwerp) but enjoyed walkabouts of the architecture, history and museums very much. We had limited time in Brussels so weren't able to give it the time it likely deserved, so it wasn't a favorite, but can highly recommend exploration of the other three. Bruges too often gets underserved short shrift as a tourist trap because of the day-tripping crowds but we found that most of the hordes avoided the better of the attractions - Groeningemuseum, Sint-Janshospitaal, Jeruzalemkerk, Onze Lieve Vrouwekerk (not just for Mike's Madonna) etc. - so we rarely felt overrun. The early mornings and evenings, before/after the day trippers clogged up the Markt and Burg and the boat tours were churning up the canals, were wonderful times to be out-and-about with the lens.

It helps to do some reading beforehand.
Belgium beer is a definite bonus. 🍺

Late-afternoon beer o'clocks are a ritual when we travel but they were especially happy in Belgium. Oh my. :O)

@Kathy Thanks for your advice! I'm still in the early planning phases and hadn't really considered Antwerp or Ghent. For 9 days, how many days would you spend in each place. I'm not sure if you saw in one of my previous posts that I would like to try to fly home from Paris, so I could squeeze in Versailles and Normandy Beach. That may have to wait for another trip

@James E. Lots of great advice. Thank you!

We were in Dresden and Prague this past Jan/Feb. We had 8 full days, and spent one of those over in Leipzig. We are not slow travelers at all, FWIW. I adored Dresden! I wished we had more time for Leipzig. We had 3 days in Prague and wished we had at least another day. The only downside to Prague was the crowds. I was stunned at how busy it was. Dresden was pretty much void of people, so I felt like we had it to ourselves much of the time. Prague though felt like we were at a theme park, with so many people. We got up very early though and enjoyed it in the mornings before everyone else was up and out. That part was magical and I would love to go back just for that.

@mikliz97 Thank you for your advice!

A really nice thing about Romania is that so many of the buildings have small plaques indicating the century of their construction, and in some cases also the century of major remodeling. I was impressed by the prevalence of those plaques.

We have been to the Normandy beaches in mid February. Yes it was cold and rainy, but that did not detract from it one big and it actually gave some perspective to it. I would go there during that time of year again in a heartbeat. But then again, we also went to Scotland and London in early February and loved it.

@mikliz97 Thanks! I was in London this past February and had a great time. I went to Stone Henge and it was cold, windy, and a little rainy but I still had a great time!