I only have 3 days in late december...which city is best to visit?

Prague if you can stand the crowds and not get ripped off. Budapest for a quieter stay. Which city attracts you more visually - check picture books and decide.

WK

Prague will have more Christmas magic!

My personal favorite, Prague. In fact, it is one of my favorite places on the planet. I've been 3 times and love, love, love it. The museums and art are awesome and the city is magical.

you won't go wrong in either city as they both have there charms. Prague shades it during the day, but Budapest wins at night with its magnificent floodlight views if the castle etc. I've experienced Budapest near Xmas and there are nice markets (e.g. at Vorosmarty ter) and decorations so its a nice Christmasy feel.