I do not know all the details on either program, but I do know that PSA is trying to be more flexible than Envoy's when it comes to how you pay "your share". With Envoy, I believe they expect you to use your GI bill to cover a portion of the cost. With PSA, they are saying "You have the choice on how you want to fund getting your flight hours, no GI bill use required. Plus you can build hours on your time, as long as you complete in 3 months." I believe if you choose to not use the GI bill to fund your portion, then you can either pay out of pocket or receive a reduced bonus. The reason for doing it this way is so folks who the GI bill is worth more to them if they pass it on to their kids can still have an option without having to use up a portion of it. The GI bill has monthly limits on it with respect to aviation training that are well below that of what it is worth if it is used at a university.
I'd go ahead and call the recruiters and get the gouge directly from them as this program is very new and I don't know of anyone who has entered into it yet.