Yeah, way too many variables for a blanket answer.
For instance, if you compare a Str-24 +5 Greatsword Fighter-15 Power Attacking for 7 (so they have the same attack bonus; 1 for the weapon enhacement difference, 4 for the BAB difference, 2 for the TWF penalties) with a weapon-finess, Dex-24, Str-6 Rogue-15 two-weapon fighting with +4 shortsword attacking that same Balor (they're on opposite sides of him), and the Balor's DR applies, ignoring crits...
2HF: 2d6+10+14+5-15 average 21 damage per hit,
TWF: 9d6+2-15, about average 18.5 damage per hit (a little different than that, actually, but not enough to matter)... but six attempts, rather than the fighter's three, all at the same attack bonus; Rogue gets 37 damage in for each 21 the Fighter does in this instance.
If the Fighter gets Weapon Focus (Greatsword), Weapon Specilization (Greatsword), Greater Weapon Focus (Greatsword), and Greater Weapon Specilization (Greatsword), and power-attacks away the attack difference again, the Fighter gets +8 damage, bringing him up to 29 damage per hit, while the rogue keeps the 18.5 twice as often - 29 vs. 37, Rogue wins. Remove the DR for both, rogue very wins; both spent four feats on this - for the Rogue, that's Weapon Finess, Two-Weapon Fighting, Improved Two-Weapon Fighting, and Greater Two-Weapon Fighting; for the Fighter, that's Weapon Focus (Greatsword), Weapon Specilization (Greatsword), Greater Weapon Focus (Greatsword), and Greater Weapon Specilization (Greatsword). Of course, that's basically it for the Rogue's feats (he's got two or three others available, depending on race), while the Fighter has only spent four of 14 or 15 feats on it.
If you remove DR from the equation, The rogue blows the Fighter's damage out of the water (fighter get a +15 damage per hit, but for every hit the Fighter gets, the Rogue gets two... and also gets the same +15 damage per hit).
But the Rogue is squishy, and shouldn't be in melee anyway. The Fighter's choice of power attack isn't optimal (it's for making the comparison easier), and so on. If you don't ignore crits, the Fighter can get downright nasty when it happens, as everything doubles, while the rogue gets an extra... 1d6-2.