GMATPrep Quantitive vs GMAT Quantitive

I don't think many people say that real GMAT quantitive questions are harder than those of GMATPrep. They do say that real GMAT quantitive questions are harder than those of Official Guide (which is true to a large extent). OG questions are quite old and not very representative of today's level i.e. an average student today is smarter than an average student 10 yrs back so a 500 level question today will be a little harder than a 500 level question some yrs back, in my opinion. Also OG has a lot of lower level questions while if you are smart in Quant, you will get to see only 2-3 of those low level ones in actual GMAT. That is another reason why actual GMAT tends to be hard.
GMAT Prep questions are indicative of actual GMAT questions since GMAT prep test is also adaptive and probably uses the same (or similar) algorithm as actual GMAT. GMAT prep test has many treacherous questions with tons of holes for you to fall through (if you are at a higher ability level). Still, the reality is that many people get less in actual GMAT as compared to their scores in GMAT prep test. Some of it may be attributed to nerves while a small part of it may be attributed to a few very tricky question which throw people off in actual GMAT