Traveling to Neuschwanstein Castle from Munich

The bus day tours are really overpriced. It's easy to do it on your own for much less with regional trains and a Bayern-Ticket. The trip from Munich to Füssen by train and the bus from Füssen to Hohenschwangau, where the castles are, takes about two hours each way and is completely covered (Bahn and bus) by the Bayern-Ticket.

However, there is too much to see in Munich. With only an evening and a day, I would stay in Munich.

What does the day consist of on a day tour?

I assume you are talking about the Grey Line bus tour. It includes Neuschwanstein plus brief visits to Linderhof (~1 hr) and Oberammergau (~½ hr). IMO, they added Linderhof and Oberammergau just to make the trip difficult to duplicate with public transportation and, therefore, justify their very high price (almost $70 w/o castle admissions). One hour at Linderhof is just long enough to tour the main building, but nowhere near long enough to see the extensive grounds (I spent half a day there). Half an hour to "explore Oberammergau" is a sick joke. You basically spend almost 7 hours on a bus in order to spend 3½ hours at Neuschwanstein.

An evening and a day...

Well, the independent trip to N'stein and back will require most of a day. You'll walk at least an hour to the entrance and back from the final bus stop. It's a 30-minute tour. The entrance + reservation fee is around €15 ($18.) the round trip by train isn't free either. So if you think of time as money, and you add that cost to the admission fees and other expenses, you are paying a whopper of a price for a 30-min. tour that, in the opinions of some, isn't worth the trouble. But it is a famous castle, right? Not quite. It's famous alright, but it's actually a residential palace completed just before the dawn of the 20th century. The faux castle facade is a nifty bit of deception.

http://www.dw.com/en/is-neuschwanstein-all-its-cracked-up-to-be/a-17887035

I would stay in Munich. There's a palace right there - the birthplace of Bavarian king Ludwig - with more to see and do:

http://www.theworldisabook.com/16991/munich-with-kids-nymphenburg-palace/

Yes, spend your much too little time in Munich rather than traveling to castles. Munich is a wonderful city - sign up for a Mike's Bike Tour to see some of the highlights of the city.

Don't get me wrong, I think Neuschwanstein is a great place to visit. I just think that with such a short time in Munich you shouldn't venture anywhere outside. I wouldn't even suggest going as far as Nymphenburg or Dachau with such a short time. Visit Marienplatz (Frauenkirche, the Glockenspiel, Kaufingerstraße, Victualienmarkt, Hofbräuhaus). You probably don't have time to visit Deutsches Museum, but the Münchner Stadtmuseum is close to Marienplatz, and I have always found it interesting.

When Excalibur opened in Las Vegas, they touted it as looking like a medieval castle (it's actually based on Neuschwanstein), but I don't think most people visiting Neuschwanstein today, if they know anything, expect a medieval castle. It is only a palace, but it is gorgeous and it looks more like a castle than some castles I have visited. There is a lot of resemblance to the Marksburg, which is a real castle.