Most importantly though: trains are so much faster than buses! No traffic jams, no delays (for the most part, at least) and traveling at high speed makes train travel much faster than buses. On a train, however, you can bring all the stuff you want, including things like pocket knives or corkscrews which you can’t bring on a plane. Train travel in Europe is brilliant. I use them all the time. In fact, I just returned from Italy and traveled by train from there to Berlin!
We took a combination of the regional trains in Italy from Verona to Venice at €10 a pop, a private sleeper bed compartment with the Austrian Night Jet train (complete with private toilet, shower and towels) including breakfast, sparkling wine, water and a goodie bag at a cost of just €103 each! And the fast ICE train from Augsburg to Berlin in First Class at a mere €26,91 per person via Deutsche Bahn /German trains (DB)!
Generally, trains in Europe are no problem at all, they're safe, pretty clean, mostly on time and everyone uses them. However, not all trains include a restaurant car, WIFI or charging outlets so keep that in mind.