VPI or Pro-ject

Holding value is only important if this is a temporary stepping stone to a better table in the future.

Both the VPI Prime and Project Extension are both very good tables.  You should listen in your system in your room with the cartridge you intend to use. 

I typically recommend VPI, but in this case, you should try both. 

I'm leaning strongly towards getting a Prime. 
My next challenge will be in getting a cartridge - I haven't a clue. 

What's your budget for a cart?

I'm awaiting delivery of my Prime turntable to replace a Scout.
As for cartridges, Lyra and Dynavector are always popular choices for VPI tables, though many others work well also. Typically, you want to make sure the cartridge has a body weight greater than 7 grams, and a compliance higher than 10.
Currently I am using a Ortofon Cadenza Bronze on my Scout. I enjoy it, and plan to keep it on my Prime.

I haven't heard the Pro-ject tables, but I have heard a few Regas. How did you like the P3?
I'm guessing you did not care for it that much, or else you would be asking about a P8/9/10 in this conversation.

As for trying these tables, well good luck with that. Even if you are lucky enough to find a local dealer who carries both, odds are his room and ancillary gear will be different from your own. I've found that there is no substitute for listening in your own room with your own gear. I doubt you will find a dealer who will let you try both in your own system.

So just read some threads and pick the one you think will sound best. In the end, I don't think you can lose, as they are both fine turntables.

Happy hunting,
John