I use 2h weapons, or at least have for 10 of my 11 gens. They're are several reasons for this, I shall list them, as follows.
1. When I first played c-rpg back in the scary pre-upkeep days I was new to multiplayer warband. I played 1h shielder and I found the amount of effort and swings required to down someone quite maddening. I then poodled off to native to learn how to rack up the k/ds the 2h pro's were getting, or at the very least kill something in less than 6 hits.
2. 2h are sexy. They look boss, no denying. Not to mention the "Cool" factor that big fucking swords have in popular culture. A choice between an elegant piece of sharpened steel handcrafted by a master sword smith for the sole purpose of war or a bit of wood with a common smithed axe head on top? Didn't take me long to chose.
3. They are easy to pick up and play with. Even I, using a heavy bastard sword on my second gen character did considerably better than I could have hoped. Competeing with the top tier players is not easy to pick up, however.
4. They have the best animations. Not in terms of there aesthetic beauty but taleworlds kind Of fluffed the extra reach you get on ALL directions of swing, compared to the other weapon types.
5. There is nothing more thrilling than an evenly matched 2h duel. This is my personal reason for staying 2h for so long, to me a good, hard fight against a well matched opponent or 2 is the reason I love Warband. Especially when you beat the long odds and walk away from an encounter with a top player or multiple players.
I concede that 2h combat is the most powerful and easiest to pick up. The most boring, definitely not, and if you aim to fight players you recognise as good or better than you are I find the mixture of footwork, manual blocking and the awesomeness of having 5ft of steel singing in your hands to be the crowing glory of the warband franchise.
My 2 pence anyways.
Tl:dr 2h are powerfull and easy for beginners to learn but are a lot of fun for experienced players too!