Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General One-handed + Shield vs. Two-Handed.

In my experience, it's pretty straightforward.

One handed will never do as much damage as two handed.
Two handed will never be as tanky as a shield-user.

My sword and board has a 70% chance to block any melee attack. The only thing he gives a shit about is cc.
Meanwhile my 2-hander is dealing 2000 damage crits with bully.

Honestly, if you aren't having problems with survivability (I'm not) then go 2-h.

Also worth noting that 2-hander can make use of Anaconda as well, as there are 2-handed maces in the game.
Also also worth noting than most Man-At-Arms talents are more efficient if you're using a 2-handed weapon. Flurry = 4 hits for 8 AP. Much more valuable when you're using a slow weapon than when you're using a fast one.