what am I missing if I drop Budapest from Prague-Vienna-Budapest itinerary?

If you skip Budapest, you will miss the most interesting city on the planet. A highly biased, but, nevertheless truthful opinion.

Budapest is worth keeping in your itinerary, different from the others, behind the Iron Curtain for so long.

The obvious answer is you'd be missing Budapest.

And that may sound snarky, but I mean it sincerely and supportively.

No trip can cover everything on our bucket list or even everything in the vicinity of where we are going. You always have to sacrifice one thing in order to do something else. And that's okay, and there's nothing wrong with it.

Don't think about what you'll be missing. Concentrate on what you will be seeing and enjoy it all! Have wonderful experiences and bring back fabulous memories!

I love beautiful Budapest and from a historic standpoint, those three cities fit together nicely as they were all part of the AUstro Hungarian Empire. Only you can decide how much you can handle. I think all three in 2 weeks is doable, but that's me. Can you add a couple days (and Budapest)?

suki: Budapest was behind iron curtain not any longer than Prague; actually slightly shorter.

I have been considering adding 2 days and starting in Budapest rather than ending there.
One challenge is I found in a recent trip to Spain that I much preferred the secondary towns like Toledo, Segovia and Cordoba to Seville or even Madrid. So the thought of more time in a huge city doesn't much appeal.
Another thought is a smaller city/town in Hungary for a couple of days accessible from Vienna. Get a flavour of the Hungarians without the same level of tourism. I need nature breaks and some down to earth experiences.
What do you know about Sopron, Tata, or Gyor?

Haven't been to Tata. Liked both Gyor and Sopron but definitely preferred Gyor. It has a somewhat larger historic district and a lot of small art museums that I enjoyed.

If you want to see Pannonhalma Abbey, check carefully once in town to be sure you'll be able to get inside. The T.O. did not warn me (may not have known) that the day I chose was not a good one. The abbey was closed to the public until 2 or 3 PM, and what made it worse was that there was a bicycle race in the area that altered the bus route, so I had a hot uphill slog before I found out that the abbey was inaccessible.

I liked Budapest a lot and hope to return, but I would not try to squeeze those 3 cities into a 2-week trip. Since you are not a great fan of large cities, I'm guessing you're not thrilled with crowds, which by all accounts are worse in Praque and (tiny) Cesky Krunlov than in Budapest. Not speaking from experience since I won't hit Prague for about 2 weeks myself, but I'm expecting central Prague to be pretty overrun.

I am hoping April is less crowded, but there is a lot in Prague I want to see. There are also plenty of day trips and not necessarily Cesky Krumlov. There is Konopiste, Kutna Hora, Olumouc, Brno, or Kromeriitz. Some are a little far for a day trip, but could be an overnight to Vienna.
It isn't even the crowds,it is the added logistics due to size. Smaller towns are more walkable and easier to get one's bearings.

Prague is ungodly crowded year round. Possibly the only more crowded place in the Czech Republic is Cesky Krumlov between 10am and 3pm. On the other hand Budapest isn't a great museum town. Its more about the culture of the city than dead things under glass. Vienna is a wonderful museum city. Budapest does have an outstanding collection of Art Nouveau buildings, but alas, many are not restored. Here are some that are in pretty good shape. https://io9.gizmodo.com/5982737/this-is-why-budapest-is-famous-for-its-art-nouveau-architecture

For castles, nothing beats the Czech countryside............ except maybe Slovakia.

Thank you all for your feedback. I'll take them into consideration and keep planning.

I hope you decide to keep Budapest, you won't be sorry--it's my most favorite place on earth and I've been there 4 times in as many years, looking forward to next May already. If you love birds you might enjoy spending time on Margit sziget, the little island in the middle of the Danube near Parliament. There's a little zoo/animal sanctuary (peacocks, water fowl, various chickens and geese, crows, rescued eagles, etc) of sorts there and I love to see the nesting storks--they are quite special to me. You can get within 4 ft of them, they have free reign and their habits are fascinating to observe.

You mention an interest in Tata--I went there 2 years ago as it's the town my great-grandparents came from. Easy train ride from Budapest, though I would have done better being taken there by a guide or driving as there's interesting stuff to see outside the town proper--an English garden, lake, castle and more. The town itself was interesting to explore for a few hours, including time spent in the cemetery looking for Katonas to further my genealogical research.

Other day trips I've done include Godollo, Szentendre and Pecs (at 3 hrs each way it's a long day but certainly do-able).

With so many great options of cities large and small, my advice is to make the trip as long as you possibly can! This part of Europe is also fairly central and easy to reach, so you very well be able to get there again, versus some cities with fewer transportation options (like Dubrovnik).

Thanks all. With six weeks vacation, it isn't the inability to carve out time, it is the trying to find a balance. As a solo traveler, I also tend to be self reliant, which means I don't take tours...even day tours, and I don't build in any 'no days' for mental breaks. I found out the hard way in Spain this Autumn that 6 moves in 3 weeks was not a good idea for a recovering body, so I am trying to learn from that. Body is better but still an aging body, and we are sometimes our own worst enemies.
This trip will be minimal moves, day trips (some via tours) and possibly a shorter length.
James E did mention Slovakia for castles..... maybe I can come back for a Slovak/Hungarian combo. That or combined with Croatia.
I'll keep working on an itinerary before committing to flights.

Budapest is our new favorite city, and we are very comfortable when there. I would drop the much more expensive Prague from the list.

I chose Budapest over the others last November and have zero regrets. Now I may return to Budapest or try a new place. I love people more than museums so Budapest was perfection!

Thanks all.
I think I am going to put this off until next Fall or Spring 2020. However, I have done some starter research, and maybe if the energy is there, and a good seat sale comes up, I might do it short notice.
I will aim to include Budapest. I am not so approachable when I am a traveler, so at times, the better parts of travel escape me. I will admit that the plains in Eastern Hungary also have an appeal, thus the consideration of shelving Budapest to a time I can include more of the country.
We'll have to see what is decided when the opportunity arises.
Travel Man, you are correct that no one knows what is in store for us. That is why I ensured I ticked off the big bucket list items a few years ago. The rest will happen...or not. No regrets from here on forward.

If you have to choose between which of the three to drop, I would say Prague. Therefore, within that two span of time my suggestion is that you focus on Vienna and Budapest.