i use BP Ultimate for 2 reasons:
firstly, I used to use Optimax, tried BP once and the car seemed to run so much better (got no technical stuff to back it up lol...just felt better)
secondly, convenience! Both the BPs in Canberra that have Ultimate (yes, we have a whole 2 of them!!) are 24 hour, and one is near my home, and the other is near my work. And since i work nights, it's perfect