A bit more info...
Wow, this post took off like mad.
First, kreynolds. Nice feat. How long have you been saving that one to drop on some unsuspecting lurker??? I'm honored.
Try this one on for size:
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Allright, regarding my comments at the top of this thread. The example we use in our group is a 20th+ level half-orc fighter, with a 34 Str, with weapon focus and weapon specialization. He can choose to use two Shortswords or a Greatsword. Base damage and crit range is identical. (I'm not sure what a Herculian Greatsword is, but I know I wouldn't want to get hit by it). The weapon specialization on both hands is pretty much offset by the -2 to hit, until higher levels.
Very good, relevant points were made by too many to site individually.
1) To use two weapons, you must invest significantly more feats.
2) These feats are of benefit to ONLY the two weapon style.
3) Many combat feats benefit both styles (Cleave, Power Attack, etc.)
4) Two weapon style will lag, just slightly behind two hander style, particularly in the middle levels (say around 6th - 12th. But, once the magic starts ROLLING in at higher levels, it's no problem equipping yourself with a couple of badass weapons.
5) Whirlwind Attack, Attack of Opportunity, Spring Attack, and Charge Actions (including attendent feats) ARE better for the two hander style, particularly until Epic. These are a good diferentiator in the mid to high levels.
Here is where the challenge comes in:
Rokugan Feat (I apologize I don't have it to reference): allows full strength bonus in both hands.
Epic Feat: lose the -2 to hit and gain a full complement of attack actions in both hands.
Epic Feat: Grants a "rend" like attack if you hit with each of your two weapons for weapon damage + 1.5xStr (ouch), in addition to all the rest of the damage you do.
Epic Feat: "pounce" charging feat that allows you to make a full attack action on a charge, on the first round of combat. Not completely giving away the farm, but certainly giving up some of the key benefit.
So, the point is, although the damage is close up to around 12th level, what other feats would you suggest for two hander stylers, that would benefit only two hander stylers, to make up for the difference.
I think Power Lunge is a good mid-level example of this kind of feat.
A feat that would enhance attacks of opportunity would also be more beneficial to two-handers. Perhaps something relating to "reach" for two-hander weapons. This might also help to mitigate the over-powered spiked chain.
There have been a few other really good suggestions. Anyone else?