Have you considered that you might also have things stolen from you on buses?
It is pretty easy to grab something that isn't yours from the overhead bin and hop off a bus when it stops. I had a bag stolen from me when I travelled from Berlin to London on a bus several years ago, the bus stopped in Hannover, Eindhoven and Amsterdam to let people off and on and during one of those stops it must have happened. Luckily it was only my empty lunch bag. Busabout does similar stops if I read their website right.
I have also ridden trains and buses and given the choice between 10 hours on the bus or 12 hours on the train I will always take the train. Riding the train is so much smoother, there is far less jostling around. Consequently it is less tiring and you can sleep easier. Train is also much faster in most cases and goes to more destinations.