(...)
Conclusion: slow WPF helps actually hitting people.
Could I be right?
Nope, not in my experience. But i guess that's subjective.
But try this: buy both a light and a heavy lance and see which one you prefer. The heavy lance is much slower, which makes it harder for me to stab heads. But it does have a bit of extra reach.
Going 'polearm only' is a good choice for cav.
Think about what playstyle you prefer. Test it out. Do you like long, straight runs with a couced lance? Then heavy lance and a courser is great. Do you stab at heads while dodging arrows and pikemen in the mids of a chaotic battle? A light lance or even a militairy fork with a steppe horse is great for that.
It all comes down to personal preference and playstyle.
My personal prefence: 1h + shield and a steppe horse. Or if i go pole, i'd use a steppe horse and a light lance probably.
I'd allways go for max wpf in pole though. More is better. A faster stab = more stabs = more kills for me.