The point of the feat was to dual wield the same sized weapons instead of having to use a mere light weapon in the offhand. OTWF doesn't give you full strength on offhand attacks either. The difference in damage is the current 6d8 versus 4d6 with a light weapon.
Just going on averages thats like, what, a difference of 15 damage per swing with 3 swings on offhand? Maybe average-ly rounding to a difference of almost 50 damage on a full attack between light and non-light.
Thinking about that though reminds me I could have actually gotten a pair of one-handed weapons instead of a pair of daggers for basically the same price
Oh geez I just realized I couldn't even make use of the pure metal shield even just for the AC bonuses because I can't TWF with it as that is a property of the Pure Mythril specifically
Blaaaaah, if this persists I'm probably just going to be donating all this refunded cash
Or something for Wisdom and still throwing the rest at charity....
And then I realized I wasted 5k gp on a second dagger when I bought a mercury pistol that could be shapechanged into a second dagger anyways. Refunded that yay I'm dumb