Iīve enjoyed pretty much all the C. European cities I have visited.
BTS is nice and quiet and near Vienna, which I also recommend. IMHO, traditional food in most of the Central European countries (Austria excepted) is generally boring/devoid of spices (thatīs especially true of Poland). KRK is great, too, and I have heard good things about Kosice (but never been there). I ve been to BUD in winter, and I kept thinking that good weather would make this a really good place! So there is lots to see, and every city has its merits. You can do worse than avoiding chain hotels and ones priced in Euros/dollars (my strategy is to go for the best one that quotes a price in local currency).