Gmatprep 2006 version and 2011 version

Guys,

Is there a difference between the level of difficulty of questions from GmatPrep 2006 version and 2011 version? I have given 2 CAT tests from the GmatPrep 2006 version and got a score of 710 both times (Q49, V36 and Q49,V38).

I am a bit worried whether the questions in the GmatPrep 2011 version are a bit difficult when compared with the 2006 version or not.

If anybody out there has done a good analysis between the 2 softwares, please suggest me the difference in the level of questions for both Quant and Verbal.

One observation: I found the RC of GmatPrep 2006 version pretty easy to comprehend, but I have heard a lot about the increasing level of difficulty of the real GMAT RC passages. Any comments here??