USPS vs Pat Salmon

I am looking for specifics on benefits or cons of working for each, from drivers who may work or have worked for either. I have a seasonal offer from the post office, and an extra board driver offer from Salmon. I spoke with a Supervisor today from the post office, and he stated all 5 seasonal drivers from last year were offered a full time gig after the holidays, which is great. He said any full time opening after the holidays is first offered to those who drove for them during the seasonal rush. The problem for me is if I had to wait a few months after the holidays for that offer. Salmon starts off as a full time extra board driver, but some weeks you may not get called, or limited at best lol. So, that's kinda the dilemma I'm in. Obviously, working directly for the post office would probably be the better option, I'm guessing. Any insight you all may have would be greatly appreciated. I don't know if the benefits/pay at Salmon would be the same as the actual post office, as they are the largest mail contractor. Thank you in advance.