Low bar all the way. Discovered it in college and haven't looked back. Weight is more stable and you can lift more.
It's a goal-dependent decision, especially when you get into the Olympic vs powerlifting. That being said, the majority of people out there have lost the mobility to squat with a vertical chest and would benefit from low bar back squatting initially. With time and persistence, an athlete should look to master both types of squat techniques with a bias toward the type that will benefit their sport the most.
I am in favor of the high bar placement for the pure reason of increased vertical torso from that of the low bar and the ability to squat for more depth. I think the low bar only applies directly to powerlifting since the intended goal is maximal weight. If sport performance and overall increased mobility and athleticism are the goal, I think there is no question the high bar is the way to go. That is how we like to teach it at PTG!
This is entirely conjecture on my part, but I believe Rip would say that the entire reason for lifting weights is to get strong. The more vertical the back angle the less stretch is places on the hamstrings, involving less muscle. Since Rip teaches a below parallel low bar squat with a moderate stance, some might argue that it's deep enough. A lot of athletes can squat even deeper than that but it is usually a matter of what they had to relax to get down further than a few inches below parallel. I'm not necessarily trying to pick a fight, but I have a hard time believing how a more vertical back angle translates into sport performance. Any contact sport is going to based the 45 degree angle for maximal force development. Also the first several steps of a sprint. A case could be made for basketball because in a game situation players are often looking up and don't use as acute a back angle before a jump, but will during a vertical jump test. Any situation where an athlete can more effectively use as much muscle as possible is a win. I don't think the squat really builds athleticism like something like the power clean potentially does, but it will certainly build a stronger athlete.