What unit do you use as the mainstay of your army later in the game? (post patch)

Spearmen are good all-around but need upgrades to be anything worthwhile later on. Pikes are great for anti-cav but not good for much else & Swiss pikes are expensive & you get them only in Switzerland. Halberds are too slow and their Swiss varients don't make good mainstays. Billmen are good but only when you play English. I tend to stay away from sergeants, some people say they're good, and others say their bad...

What do you use?