As the owner of both, and all variations (P7 PSP, P7M8, P5 and P5C), if given your choice I would definitely go for the P7.
If you've never shot a P7, once you shoot one you will be hooked.
That's not to say the P5 isn't a great gun, it is.
The P5 and P5C are conventional DA/SA, not DA, and were never offered in DAO.
BTW, the P7 is a fair price, if as described, but it should come with the original box, manual and scraper tool for that price. As well as both magazines. PSPs (the one you describe is a PSP), usually command less money because they have the butt magazine release and no heat shield. If it is a flush mag release, I believe they are more desirable. I'd still offer $800, but it depends on your market. The P7 PSP (No heat shield, butt mag release) is no longer in production, and new production P7M8s are commanding $1200 from dealers.
You should be able to do better on the full size P5. There were closed out a few years back for $449-$495. I wouldn't pay more than $750 for a NIB P5. A P5 Compact commands more and you can buy a brand new one from Val at Gulfstream Sports or Earl's Repair service for $900. P5s are no longer in production, but the P5C is.
My .02 worth.
Regards,
James