Yeah, drinking on the train is nothing short of madness.
On the Bratislava/ Vienna thing; I would say that both are worth a visit, but that if you're short for time then it would have to be Vienna, seeing as it's a genuinely breathtaking city. I personally had a better time in Bratislava, but that was purely circumstantial. We were givena guided tour of the city by some locals that we knew through someone's sister which was probably the reason why I enjoyed it so much, but they were puzzled as to why we had decided to go. According to them; everyone leaves the city at the weekend, which I didn't believe until we walked through the city centre on the night of the champions league final and the place was deserted.
If you do go to Bratislava, however, I would recommend Hostel Possonium (It's 5 minutes from the train station and has a basement bar themed like the film 'Hostel') and that you find your way up to the big monument on the hill as the views from up there are pretty spectacular.