The cbv / pgn are out.

Actually, in this case, I meant that Black was striving for a win at all costs. But you're all correct that normally, we talk of two results being white playing for a win or draw. I should have been more clear.

If I had a must-win situation as Black and had both the Benoni and the Tarrasch in my repertoire, I would almost certainly choose the Benoni.

Agree. Which two results are we talking about in the Benoni? Win and lose? I though that to use that term you had to be speaking of winning and drawing, with losing no longer likely.

Anyway, even at the highest levels one side can win even in those openings with the most drawish reputations. Looking at world championship matches alone, Alekhine beat Capablanca in the Exchange French, Botvinnik beat Tal in the Exchange Slav when Tal was trying to draw, Lasker beat Capablanca in the Exchange Lopez when Capablanca had only to draw,  and Anand beat Topalov when Topalov over-pressed in the Lasker QGD, even though Black in that opening "is hardly in danger of earning the full point," as Karpov sarcastically remarks.

Statistical outcomes really do vary in this respect, and it can be frustrating to draw with a weaker player where the position is difficult to unbalance. Surely the Pirc allows White more solid options than the Triangle System, so I agree with Eric.  But statistics are only determinative over large groups of games. "Playing for two results" in a single game against an equal opponent requires monumental technique and is very far from being a sure thing.

The excerpt looks really good!

Try that strategy in the King's Indian or the Benoni, or even the Grunfeld. See how you do against an equal opponent. There are plenty of openings where Black plays for two results and if White isn't up to the fight, white will lose.

I agree that the Tarrasch isn't one of those do-or-die openings. It's not necessarily a negative, it's just a feature of the opening that Black is playing a bit more safely. Even if one side loses the IQP, it's often not the end of the world. There's quite a large draw margin in the Tarrasch. But it still rewards the Black player who wants to develop his pieces and get on with a game where either side can still win.

"On one analysis, White drawing if he plays badly and generally winning if he is a stronger player, is something which happens in every opening."
I don't think I agree with this