Here's the damage die conversion for bigger weapons:
One-Handed
1d4 > 1d6 > 1d8 > 1d10 > 1d12 > 2d6 > 2d8 > 2d10
Two-Handed
1d8 > 2d4 > 1d10 > 1d12 > 2d6 > 2d8 > 2d10
So most of the time the average damage increases by one point, or seven points when using a 7[W] attack. The biggest increase...