I will post gpuz/cgminer screenshots if you would like of my gpu (7750) running script and x11 algos. I don't have a watt meter so I can't measure power consumption but one can assume lower temps, lower watt usage.
Yep, i mean nobody doubts that mining x11 with the current "widely known" x11 miners we have... uses less of the cards resources than scrypt or scrypt n, scrypt jane etc. So it does use less electricity and outputs less heat.
However, read the car analogy in the OP to see what we are really asking here.
I saw your car analogy, and I can't quite really give a solid answer. I mean, if everyone is using that algo to mine, what does it matter someone is mining "faster" as it is all relative to the algorithm. IMO, we should mine the most efficient algorithm energy and heat wise, as your hash rate is proportional. This does make ASICS easier to make as the more efficient an algo is, the easier it is to ASIC.