Which turntable? Pro-Ject or VPI?

Neither, 

Just buy a used Rega. Every jump is a big improvement in sound. Since the the new NAIA was just released in the US there should be some deals on the lower models. After that,  the cartridge and setup are the main thing. Rega and the new Ortofon carts sound and fit perfect without shims. If you want to really step it up get a Hana cartridge. You will need to shim it but it’s worth it. All the way down to the Hana SL/ SH. I know this is going against the group but this is the way you should go. 

Well if you really want quality, buy a Kuzma.

Between the two choices, VPI all day every day.

The ad listed is a great deal. I’d jump on it myself but am happy with my current turntable. 

I own an HW-19 Jr and an HW19 Mk-1. The former was purchased new and the latter used from a fellow denizen of this forum.So, here are my thoughts;

I have a Möerch UW-4 tone arm on the Mk-1. I've retired but kept the Jr in the event I need a new motor (the Jr has very, very few hours). As far as I can tell, these sound essentially identical and they are very robust.

In other words and with the caveat of not being familiar with the Project, I have no hesitation about recommending the VPI in terms of durability and sound quality.  

I suspect you can't go seriously wrong with either of them but VPI seems to hold its value and, as someone has already noted, they're built to "mil-spec" standards. Plus, parts are readily available and there are upgrades galore!

Having stupidly owned a Project RPM 10 Carbon, I can vouch for the shoddy build quality. The tone arm wasn’t much better than the $400 Project Debut TT that proceeded it, including the same anti skating weight dangling from a bit of fishing line.