James McMurray said:
But in a world where enhancement bonuses count for sunder, GMW will count for sunder.
I wouldn't necessarily agree with that, either. This has come up in other GMW threads before.
(And I'll preface this by saying it's not what we do IMC, but we changed spells like GMW in other ways to balance them)
See this logic chain:
> Enhancement bonuses give, among other things, a +1 enhancement bonus to attack rolls and a +1 enhancement bonus to damage rolls. (The other things they give: more HP, more hardness, higher Sunder threshold, higher anti-DR threshold)
> Masterwork weapons get a +1 enhancement bonus to attack rolls. In 3.0 this was simply a "masterwork bonus" that was clarified to not stack with enhancement bonuses, but in 3.5 it's explicitly been typed as enhancement.
> However, that +1 from Masterwork doesn't let you bypass DR, become immune to Sunder, or anything else that an Enhancement bonus gives. This is clarified in several places.
Therefore, the anti-Sunder ability comes from the fact that it's the weapon/armor ability referred to as "Enhancement", NOT that it's simply a bonus of type "enhancement".
> GMW only gives an enhancement bonus to attack rolls and damage rolls. It doesn't say "the weapon acts as if it had a +X Enhancement bonus", it explicitly says attack rolls and damage.
So, using this logic you'd be perfectly justified in saying that a GMW'd weapon isn't any better for Sunder or DR than it was before the spell, because like a Masterwork weapon, it gives a PART of the bonus you get for the normal +1 Enhancement. In fact, with this interpretation a mundane weapon with Magic Weapon wouldn't even penetrate DR/magic, you'd need an actual magic weapon for that.