A cheap flight is probably a better deal (saving considerable time and possibly some money) on this route than either bus or train. Overnight train would be my second choice — only in the unlikely event that plane is significantly more expensive. Day train or bus would be my last choice.

Train is pretty complicated. Overnight train is City Night Line to Koln, then High speed Thalys to Brussels then Intercity to Brugge. Day option is bus to Nuremberg then either Intercity Express to Frankfurt, another Intercity Express to Brussels and intercity to Brugge or Intercity to Koln, Thalys to Brussels and Intercity to Brugge. All options are in the 12 hour range

You ask to choose train or bus right? Then airplane is out of question. Train is my preference. Another suggestion is watch the movie name “In Bruges”.

Generally, the bus is the least expensive way to travel, but also the slowest. Trains are faster and more comfortable, but don’t go everywhere, while buses do. Belgium has many bus lines, which are apparently not coordinated, and don’t do a good job of getting routes and times out to the tourist population. Trains do much better. I found the tourist information offices were a good source of information on bus travel, but that type of last minute planning, to me, is only suited for day trips.

Enjoy Bruges, it is one of the most charming places we have been.