If the lower mileage VX is from a private party, ask him about what kind of maintenance it has had - ask if you can see receipts of maintenance. Also check out what aftermarket parts are under the hood (PCV especially). You want to try be sure you dont get an oil eater. I'd go with the lower mileage one if all things check out.

Also, are you buying from an original owner or has the vehicle had several owners?