Originally Posted by
jphripjah
Budapest is worth a full four days. Keep in mind that the train between Vienna and Budapest goes through Bratislava, it's worth stopping off and storing your bags and at least having lunch in the old town.
There are also direct trains. But I agree that it you have an extra day to spend, a half day stop to wander through Bratislava's old town is worthwhile. I've actually made the stop you suggest, but arriving in the afternoon, staying overnight in Bratislava and leaving in the morning. I wouldn't cut my time in either Vienna or Budapest for it though if time is tight.