1. Driving - Because I am a petrol addicted American... haha, kidding. I like the flexibility having a car offers, and like seeing the countryside with the option of a detour if it strikes me. Also, my family is originally from Moravia, so driving through it (even though it is apparently mostly rolling hills and farmland) is something I've always wanted to do.
2. Devoting 2 nights to Prague, Vienna, and Hallstatt does seem a bit unequal... but we should arrive at the hotel in Hallstatt later on Monday, stay the night, see the ice cave/salt mine and the village the next day, one more sleep, then get up and drive to Vienna, arriving by noon. This is really just a "preview" trip, with the purpose mostly to get a brief feel for the places we visit and see the Christmas Markets, so when planing a future vacation, we can more effectively decide where we want to spend a longer duration to actually get to know the city... Call it speed dating for frequent vacationers.... haha.