FIT is the most important aspect. They should feel comfortable snug with little to NO movement.
After that the rise of the heel will come into play.
I got used to the fact that my Adidas Power Perfect 2 have a forefoot to heel difference of 1 1/8".
When I tried other shoes with less of a difference it did not feel as good, for me.
Huge amounts of weight have been squatted with the classic Chuck Taylor and the Adidas equivelent. There is virtually no heel lift..
Take into account though, that with a Powerlifting Squat your shins remain close to vertical. Wherein with an Olympic Squat the knees pass over the feet and toes. This is where having the heel lift in olympic shoes comes into play.
Everyone will have their personal preferences. Unfortunately, this is a fringe sport at best, so trying to find different shoes to try on is going to be a Big Pain in the Ass.
Know though, that the Adidas generally run Narrower than the Nikes.
My cred's ? I have been a professional boot/shoe fitter since 1998 as well an Olympic Teams Massage and Stretch therapist. .. so take all this with a grain of salt.