Greater Two Weapon Fighting or Two Weapon Rend?

[Khazrandir]

I recently came across this question when selecting a class feat for my TWF ranger at level 10. The general advice I had seen was that TWR is a better choice than GTWF. I've been looking into this issue in detail, and I'd appreciate any additional advice, comments and/or insights on this issue.

With some spreadsheet math, I've come to the following conclusion:

TWR almost always increases single-target damage more than GTWF.

Did I say that TWR > GTWF for everything, or that choosing GTWF is badwrongfun? No, absolutely not! In fact, my ranger will likely take GTWF for some specific reasons.

I'd like to share my fun spreadsheet calculating the damage from a full attack. (It's locked, so just click "File->Make a Copy" to change stuff around) Hopefully it may help inform decisions between these feats for other people. I've left the file as fairly bare-bones, without much frilly formatting to make it look pretty. Hopefully this doesn't bother anybody, and helps make it more easily customizable.

The spreadsheet allows someone to input their attacks, damage, crit bonuses, multipliers etc. and calculate their full-attack damage average on a single target. You can put different bonuses in each row, to directly compare.

By playing with the spreadsheet and adjusting AC, enemy DR, attack bonuses/damage, crit stuff etc... you can see that in most cases, TWR will perform better than GTWF, agreeing with what I interpret as the conventional wisdom on the forums.

However, there are cases where GTWF is the better option! The first that comes to mind is multiple enemies. This spreadsheet has no way of calculating it, but it stands to reason that if you needed to kill 15 level 1 human commoners (Why? You monster!), having more attacks is always for the better. Another obvious reason to choose GTWF is because it's just so cool to attack so many times, raining down blows on the enemy!

Curiously, another case I've seen where GTWF is better is when the enemy has an extremely high enemy AC (or you have low attack bonuses). In this case, you're basically fishing for crits, so it's very unlikely that TWR damage will ever appear. However, it's nice to have that additional attack from GTWF to keep on fishin'.

So, those are my thoughts on GTWF vs. TWR. Have I missed anything important?

P.S.
My dwarf ranger chose GTWF despite this math for the flavor reason of it seeming awesome, and the math reason of more chances at stacking Twin Thunders against those evil giants! This dwarf in RotR isn't so fond of those giants.

[Liegence]

You are correct. Two weapon rend is a nice DPR boost for 2-wep fighters. Much more reliable than GTW. Likely it is the single best damage boosting feat for a TWF. It also helps a slight bit in overcoming DR, which is a big problem for TWF, because it is additional damage and not a separate hit.

[Majuba]

Best reason to take GTW is if you don't have the Dex 19 prerequisite (but do have the Dex 17 prereq for Rend).

Well.. best reason other than the symmetry issue for us OCD people...

[Trinite]

One caveat: TWR only functions if you hit the same opponent with both of your attacks. GTWF might be better if you often divide your attacks up among various targets.

EDIT: Ah, I see that you already mentioned this in your post. Good call!

[Kazaan]

GTWF is just not worth the feat slot. Spend a feat for an extra attack at -10? Thanks, but no thanks. I'll take Rend any day because, even if I'm dividing my attacks, I can always reserve two attacks for that one enemy to which I really want to apply Rend (ie. the major threat) and just divide my remaining attacks among the fodder as needed.