yep, its true, all round they are better.
ive got a super short caged version of the ultegra, this means that it will shift very fast, and have high quality jockey wheels, which means that if they do clog up with mud, they wont be so badly effected. easier to service too as somebody mentioned
if you want a mtb mech on your road bike, go for no less than an XT, XTR (rapidrise) if you have the money