@jon
Just checked an ÖBB night train from Aachen to Vienna. On a mid week day (usually cheaper), mid class sleeping compartment and 4 months in advance booking = ~260€ round trip
Direct fliegt from Köln to Vienna, 1,30h, round trip = 65€
Travelling by train only something for idealists and people with principles while having enough money?
How about to turn it around? 65€ for train and 260€ for the flight… would also fit to the time saving.