Well, my role as a 1h without shield is very similar to my role as a 2h, which makes this comparison reasonably fair. From a weapon versus weapon point of view 2h outperforms 1h. Of course it should, but I think this is too big of a margin to be compensated by the shield. I used to think 1h was as good as 2h in a duel, but that is definitely not the case anymore. If the average shielder meets the average 2h, the average shielder is at a big disadvantage I'd say.
2h have a dual role as excellent duel weapons and functioning as a support polearm with the 2h stab. 80% of my attacks are stabs if I am surrounded by teammates as a 2h, it is awlpike long and so easy to aim and curve around teammates.
I just wanted to add that things change a lot when we are talking about top players using 1h and top players using 2h.
During the tournament, the only player that killed Atze more than 2 times was Hagur (1h) who killed Atze 5 times. I don't think that he'd perform any better as 2h. It just seems that your actions as 1h are just limited to staying patient. When your enemies try to chamber you it's a lot harder for them when you are 1h than if you were 2h/polearm user. Typical randomer will perform better as 2h than as 1h no shield because he has this random chance of actually hitting an enemy and 2h weapons deal more damage on average which doesn't mean that well placed stab with italian sword can't be as deadly as greatsword's one.
Polearms still easiest ^^. No other class has such a nice swing damage-speed-length stats with all the shieldbreaking, useful secondary modes, horse rearing and choice of weapons when it comes to length and role. Also animations are very simple and it's close to impossible to do the attack wrong. Long war axe, Long axe and bec de corbin are the top polearms that I'd list. They could go head to head with longsword imho.
There is shitload of great weapons in all classes in my opinion. Item balancers r doing some good by increasing variety.