There's also a hormonal and anaeroboc response difference. Supersetting drains the anaerobic energy system a lot more than straight-sets. This will lead to more lactic acid build up (which changes your hormonal response to exercise). The lactic acid increase contributes to you feeling drained.
Supersetting (let alone "Giantsetting")is thus a way of conditioning your anaerobic energy system in a non-sport-specific manner. Probably a good thing to do from a general fitness perspective, but arguably less than ideal from a muscle-building perspective - in the long haul anyway.
I hope the experts will chime in here, but I believe supersets will not promote as much strength-gains (and hence ultimately growth-rate) as straight sets with longer rest periods.
Supersets will promote a greater short-term increase in GH. Some say this is good. Some say it's irrelevant. Please pick the one you like.
At the end of the day, guess what? Supersets have a place: they allow you to mix it up (as well as save time). Use them sometimes - they might be a welcome change for your body after 10 weeks of very heavy weight workouts.