My wife and I are going to Vienna next summer. We want to see Bratislava, too. Would it be better to stay a night or two there or should we day trip from Vienna since it is so close?
We stayed one night. We took a lovely boat ride from Vienna early in the morning. We toured around Bratislava, and had a lovely dinner. We then went to a museum and the Blue Church the next day and left on a 3:30 bus to Budapest. We felt it was enough time.
It depends on what you want to see and do. We stopped in Bratislava for about 5 hours when traveling from Budapest to Vienna. It was enough time to walk through the old town, climb Michael's gate, and enjoy a nice lunch. Trains run frequently from Vienna, so you could easily do a full day in Bratislava and not have the hassle of bringing your luggage and checking into a new place. So my recommendation is a day trip. But if you want to explore at a slower pace or visit more things, then spending a night would be recommended.
My wife and I just got back from Central Europe. We spent two nights there and had a great time. The quality of their classical music is wonderful and we ended up going to two symphonies. Wonderful food, wine and beer at a reasonable cost.
While I was in Vienna in August I took a 1 day trip to Bratislava -- bus trip there and it included a 2 hour walking tour with a local guide, then we had 4.5 hours remaining on our own before catching a boat back along the Danube to Vienna (arranged it through my hotel). Very interesting little town - great for a 1 day trip but it would be fun to see it at night and enjoy some of the many restaurants/cafes. Well worth the time - look for the fun statues scattered about as well.
Looks much cheaper to rent car in Bratislava and just take train to and from Vienna.
Why would you want to rent a car in Bratislava?
Friends of mine spent their last night in Bratislava and went to the Vienna airport from there.