Hey Camille,
Thank you for studying with the Veritas Prep practice tests! Maybe it's no surprise coming from a Veritas representatives, but I'd be significantly more confident in the data from the Veritas Prep tests. For the tests in our system since early 2013, we've been employing "Item Response Theory" scoring and delivery - essentially the same system that underlies the official GMAT (and GRE). Because our tests are so data driven - and use that data in a manner consistent with how the official test uses its data - we've been able to report scores that have surprised even those of us who worked on the project (in our latest survey, our average score was within ~5 points of the GMAT Prep average for the students studied).
What I'm most excited about - and what's probably most relevant to you - is that our scores have mapped so closely particularly at the upper end of the quant curve. It's anecdotal, but from the pool of my own students most have been within a point on the scaled quant score on their last Veritas Prep test and their official GMAT (and a plurality were exactly the same score), and nearly all of them reported that the official test just "felt similar" to their Veritas Prep quant section in particular.
And actually...many of the most recent comments on this thread seem to agree:
https://gmatclub.com/forum/has-anyone-taken-the-veritas-prep-s-gmat-simulator-cat-exams-92320-60.htmlAs for the 800Score tests - one of my favorite features of those when I've tutored students using them is that the quant has always seemed "really hard," forcing students to really practice with time management and giving them plenty of learning opportunities as we reviewed tests. So in your taking those tests you're certainly getting a valuable experience, but I wouldn't worry *too* much about lower scores as from what I've seen that's to be expected.
And an overall caveat - don't let your highest or lowest practice test score skew your confidence (or complacence) too much. There's always a little +/- 20-30 point range on there, so you're never quite as low as your worst score and you shouldn't get too cocky based on your best score. Practice tests are great opportunities to learn from mistakes, regardless of how well you've done.