Both the PGn and the Sethn are vintage output humbuckers. In fact, the Sethn is spec'd at 7.4k and the PGn is 7.3, so in that regard they're nearly the same. The Seth's are not potted, but the PG is. The PG was designed to sound like the humbuckers in Billy Gibbons famous Pearly Gates LP. The Seth's were built to be as close to a brand new 1950's humbucker as possible; like if you could step into a time machine an go back to the late 50's and buy some Gibson PAF's off the shelf. So, they're both copies of PAF pickups.
The difference is in their wind and the tone that wind was designed to achieve. The Seth is wound to be naturally warmer, smoother, richer, full sounding with a softer high end. Like a "V" eq shape, with the highs rolled off just a touch. The PG is designed to have more midrange bite and treble presence, so it's eq is just different. The PG is still surprisingly sweet in the neck position though. I don't find the PG neck and the Seth neck to be miles apart in tone. It's more just a personal preference than anything.
I really think you could be happy with either. I didn't think to ask what kind of music you play (but nice guitar buy the way). Under lower and medium gain, I preferred the Seth, even if it was slightly darker than the PG. The Seth sounded great under high gain, but the did have a tendency to squeal. The PG won't do that. At that point in my life I wanted to play 80's high gain stuff and be Slash or Warren DeMartini or someone. I still wouldn't mind being Slash though.
The Seth is the more musical pickup. The PG is designed to be a great blues/blues rock pickup with a little extra sizzle and bite. I personally think the sound of the Seth will allow more of your guitars natural sound to transmit through, as well as your style and playing dynamics. Not that the PG covers those things up, but its just voiced differently and designed to growl a little more when you heat it up with some gain.
If you play with anything more than medium output gain most of the time, I would choose the PG, personally. If you played more blues inspired and classic rock type stuff, I would pick the Seth, again personally. Of course then, you can order the Seth lightly potted as a Shop Floor Custom for no additional charge, other than the wait time; but that's a whole nuther box of rocks. If I had my own personal choice to make again between those two, I would buy the Seth. I still play the same type music now versus "then", but if I want to play higher gain stuff now I just pick up a different guitar. Back then the LP was my only nice guitar and had to cover more ground.
FWIW, that's my $.02