Ceramic with special cages and different coatings on the cages. Some of the blowers even get more balls in a bearing if that makes sense. They used to use an 11 ball bearing and have recently switched to a 13 ball bearing. This distributes the load much better and keeps these things living at the stupid rpm that we spin them above where they are rated, lol
There is actually quite a bit of difference all while keeping quite a bit the same. I'm out of time for at the moment but will put something together later tonight or tomorrow for you as far as a comparison goes from my point of view.
There isn't a ton of data available when it come to this technical stuff, all of the race stuff is always so tight lipped, lol. It's pretty cool when you sit and think about the amount of time, money and engineering goes into an air compressor
That can be used to compare one brand to the other. Keep in mind that the majority if not any Procharger that would work for an application on a mustang is self contained. You will notice higher step up ratios ( my guess is they use a larger pulley that way to help reduce the possibility of belt slip?). The biggest things that you will notice is the lack of efficiency rating and compressor map information. Vortech releases compressor maps for every single compressor that they make and most are available on their website. Procharger has yet to do the same as far as I am aware and does not do the same SAE testing that Vortech does. Does this make one better than the other, that choice is up to you! They both compress air but not all boost is created equal
You can increase the timing in the tuneup with meth, hence the gain in hp. While beneficial you will need to have a nice system and will want to keep on top of having it full at all times. @RacEoHolic330 can probably elaborate on his meth system as it is one of the nicest I've ever seen installed. Fwiw, I've seen more than a few motors melted down from empty tank or system components that have failed.
The mondo bypass valve is needed in my opinion at any compressor stage larger than an SI. Functionality wise the Mondo valve flows more air than the plastic valve included with a standard kit. That is the only major difference. Once you start getting into the even larger valves the same premise applies, they just become unable to recirculate the air that you would need for a draw through mass air flow car.