My instructor told me that the Veritas exam's verbal section is much harder than its quant. So the Veritas tests are great for students strong in verbal. With this in mind, I'd say that a quant score from Veritas is deflated because of the level of difficulty?
I have heard from other students that the tests get easier, so some suggested to start from 5 and work their way down to 1. I personally found that the 800 score tests quant sections were more difficult than Veritas' and my verbal score was much higher on 800 than it was for Veritas.
My instructor also told me that the average of the three practice tests you take is probably a good indicator of your actual performance, depending on how far spaced out they are. No practice test is like the real thing because the algorithms that adapt to your performance on all practice tests are best guesses of how the GMAT actually works. So the GMAC test is the most accurate, too bad there's only two of them.
Just my two cents.