Rudi is surely right about the winter and Alpine conditions can change rapidly (for the worse). I've been caught a night in the ALPs with heavy snow in late February when the weather just down the mountain in Munich was nearly 70F and wonderful just a few hours earlier. As someone else said as well, however, the cost of intercity trains is now quite high and I thought if there was a family involved (eg 4) the cost of a car would be considerably less. Nowadays, even Munich to Salzburg is not cheap! Anyway so many great choices. You can't go wrong!