Buy new, as on a used bow you do not get any warrenty for service at all. I don't own a PSE but I do know they are good bows, so you got to decide on what fits you. When you buy new, you know your getting quality on your bow... and if you buy used, you run the risk of not having the proper draw length as well as damage to limbs, cables and or cams you can not see or even begin to know where they are.
My first bow I did purchase used as I alreayd knew my draw length and got a great deal or so I thought at the time..... then found out the hard way my bow needed to be restrung, as I was on a draw and all of a sudden the string started to let go..... I was lucky. It was at that point I decided never used again, but I had it all fixed up and serviced on my dime which turned into $$$$ out of my pocket. And I made sure my son who I was giving this bow to, was getting a fully inspected and re-conditioned bow - A Mathews Black Max that would last him for years to come.
Now my current bow a Mathews Drenalin is backed by a warrenty as long as I own it.
Now because I like Mathews doesn't mean I hate all the rest of the other bow companies out there. There is simply too many on the market and most if not all of our modern bows maded today are great bows, and will serve you well. But on a used bow, unless you know the previous owner or a Pro-Shop that is selling the used bow has inspected and can verify that it is sound and safe, I just would pass the used stuff on by.