I've had about 8 Belgians in the past, SEVERAL Belgian crosses, and a few Percherons (Perchons- the older name) and have never had major attitude problems from any. They were all mild tempered and fairly "big happy giants" lol even wild youngins that were barely halterbroken weren't hard to get to trust me after some patience and good groundwork.
I've found that they're pretty curious also which is a plus. I've worked around a big Belgian farm in PA and even the unbroken horses all had a curious nature and seemed to be willing to try and figure out what you wanted of them. I like both draft breeds, Belgians can be a bit heavier nowdays... but I LOVEEEEEE riding draft horses! For the most part, I've found them to be big, comfortable couches and are fun to ride bareback also