I do not think that you can say definitely for any unofficial test. I would say, however, that from what I have seen those tests might score a little lower on average. They are thought to be fairly difficult...

I have taken most of the major simulated tests , Kaplan, Veritas, MGMAT. All three do a fairly good job at providing "Gmat Like" questions. As far as MGMAT is concerned, the quant is tough, and clearly a notch (or two) above the real thing or gmat prep. Having said that, their scoring was not much off in my case (compared to my actual score). My last 2 MGMAT CAT's i scored a 670 and 690 (Q43 and Q45). On the actual test i scored a 680 (Q44) so it was smack in the middle of the two. GMAT prep works the best for most people but in my case it over scored me by a good 50 points. However i would still think that GMAT prep is the best bet for Verbal, and quant on the real test is slightly tougher (although similarly written)...Many people have said that GMAT FOCUS is a better test for GMAT simulation (current quant standard), I have not tried that so cannot comment.