I actually like bridge attacks. They are tough, but winning is much more fun that way. I usually use some heavy armor piercing inf to get at the other side. Halberdiers or preferably CFK. They can break through spearmen defending a bridge. As soon as his line has fallen back a bit from the bridge, I bring the whole army across, pass the heavy inf and engage the enemy all around the bridge. If you can push them back a bit, you can establish a bridge-head and from then it`s like a fight on open field.