For starters the volume would not be the same as you are not figuring warm up sets. Warm up would typically signal to the body the typical weight likely to be used and the range of motion and would therefore eat into reserves and count towards volume as the last warm up sets were performed.
Intensity wise, going through the motions without being able to apply 'usual' force and fatiguing early would probably,
a. Not trigger hypertrophy because of the reduced stimulus.
b. Lead to overtraining.
When heavy training is conducted and also when muscles are trained without sufficient rest there is an increase in acute-phase reaction which is stimulated by IL- 6 (Interleukin).
The immune system must not be comprimised to deal with this (but it would be through overtraining such as you mention). The immune system does work here to prevent tissue damage but it does not have infinite capacity.
Furthermore the Acute phase reaction leads to a systemic reaction which includes the feeling of flu type ailments, fevers, chills and an increased erythrocyte sedimentation rate.
Overtraining doesn't just place a localised strain on the muscles involved but the whole body, this systemic effect requires recovery through rest and proper nutrition hence careful workout and diet planning.
How about this one....why don't you try squatting 500kg's for 1 rep then the next week try 50kg's for 10 reps and tell me if you find any difference between them? Same volume...so is there any differneces between the effects?
To answer your question the 2sets 6x a week will produce faster hypertrophy. However, you must be 3x more careful about how hard you push yourself. With 2 sets your workout should be very brief with no more than one exercise per major muscle group. And not too many iso's either.
You should post that curl program up...somebody will try it...you could make the argument you've raised...and you'd still be wasting your time....how about this then...there is no 'optimal'...it either works for you or it doesn't. I am not trying to be glib or take the piss it is just that your asking a question to which there is no right answer.