17th level Fighter/Ranger. My Kensai focus is axes, my Tempest and Oversize 2WF ability encourages me to use one in each hand. My favorite is Vorpal with a Meteoric Star Ruby (high damage, occasionally).
But then I got the Banhammer, which is Improved Vorpal, against nearly everything (including Bane damage vs constructs, undead, and outsiders).
But it's a hammer. So my Kensai abilities don't give it all those attack bonuses. But it's so powerful I should use it, whether in my main hand or in my off-hand (which gets fewer attacks).
So which weapon should go in my main hand: the one with an attack bonus that's +10 higher (sometimes more)? Or the one that does Bane damage and has a better chance of instant-killing?