Help me decide on a blitz/flanker fighter, Kensai or f/m? Options

[Mongerman]

I trying to decide between a f/m or kensai for my last character. This character will wait in the background till enemies engage my tanks, then move to lay down the smackdown. Hence, the point is not to get hit, and to do as much dmg as possible.

Should I go for the extra dmg a kensai provides, or a f/m for added survibility and some extra spell casting ability?

Also, does the increase range of 2 handed weapons provide any tactical advantage? Since if not, I rather go for dual wielding for the increased damage