My two cents:

Flanders is a good place for pikemen +1 because in the 'Guldensporenslag' (Battle for the golden spurs) a peasant army clobbered an army of French knights. What they actually used was a 'Goedendag' , a heavy club with a dagger fixed on top, but since there isn't such a thing in the game, pikemen will do. The other area famous for pikeman-like troops is southern Germany from witch came 'Landsknechte' (pikemen) and perhaps Schotland from witch came 'Schiltron' troops (also some sort of pikemen). Pikemen can be good, but if you don't use them properly, they can be beaten by lesser troops.