All 2H weapons are pretty similar compared to polearms which have a much greater variety of weapons.
2H is a class in itself (duelist footman) but polearms can be used to play as cavalry, pikeman, axemen etc.
Also, polearms can be very useful even with low wpf (lances from horseback and pikes on foot). That is not the case with 2H.
I have played as a lancer (horse + lance) for like 10 generations with all points in polearm proficiency.
However I've just proven to myself that a dedicated lancer doesn't need more than 50 wpf in polearm. I'm doing just as good as I did with 160wpf.
But if you are going to use a polearm on foot you want all points in polearm of course.
This is my current build and I do really well both as a lancer and a 1h/shield-cav.
For the next gen I might get wm instead of shield and put all but 55 wpf in 2h (lancer +2h footman).
24/15
8 power strike
5 shield
5 riding
5 athletics
55 polearm
100 1-hand
And this:
A bit? Polearm loses 20+ reach because of the grip, aka from any polearm lenght you substract 20 when measuring it against corresponding 2h. Great long axe has shorter actual reach than, ie, miaodao.
On top of that you have 2h swords thrust which adds 63 iirc range. With the fantasy swords (danish etc.) you can outrange proper cavalryman with heavy lance.
2H also got better speed and the animation makes it harder to block than polearms.