Infiniti2000 said:
It's absolutely a no-brainer. Anything that gives you better damage than weapon specialization is a no-brainer. Let's look at the average numbers, starting from the minimum value at 6th level, and considering only medium-sized monks.
1d8 (4.5) --> 2d6 (7) = gains 2.5 damage, already better than WS
1d10 (5.5) --> 2d8 (9) = gains 3.5, significantly better than WS
2d6 (7) --> 3d6 (10.5) = gains 3.5, same gain as previous increase
2d8 (9) --> 4d6 (14) = gains 5, holy smokes this is huge for a feat
or 2d8 (9) --> 3d8 (13.5) = gains 4.5, holy smokes this is huge for a feat
2d10 (11) --> 4d8 (18) = gains 7, that's huge
This is true according to the rules. It is also true due to a flaw in the rules. The size weapon category table and monk size damage tables have a serious flaw in them. Instead of going from 1D8 to 1D10 for large creatures, they skip a "die" and go to 2D6. Without that "error", it would not be as significant and it would balance out somewhat with Weapon Specialization.
1d8 (4.5) --> 1d10 (5.5) = gains 1
1d10 (5.5) --> 2d6 (7) = gains 1.5
2d6 (7) --> 2d8 (9) = gains 2
2d8 (9) --> 3d6 (10.5) = gains 1.5
2d10 (11) --> 3d8 (13.5) = gains 2.5
Now, you can debate whether this is a flaw or not, but it seems slightly unbalanced, especially when you are discussing feats.
A medium D6 weapon becomes a large D8 weapon (29% increase).
A medium D8 weapon becomes a large 2D6 weapon (56% increase). Considering that larger creatures also tend to get Strength boosts as well, that's a pretty big jump.
And, I can understand why WotC might have wanted to do this (let's make large creatures significantly more powerful than medium sized ones), but this opens the door for feat abuse and other abuse (e.g. the Spell Sword in my game exclusively uses two handed weapons one handed, just so that he can use large weapons and it gets worse when he Enlarges). IMO.