The level of questions in all three books is similar - there are easier, medium, and harder questions.
The bigger issue is your strengths and weaknesses - and your current scoring level. What were the results of your last practice test? (Did you take it under official conditions, including essay and IR? If not, your score might be artificially inflated.)
You can use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/Figure out what you think you should do based on that analysis. Then come back here and tell us; we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
Note, also read these two articles BEFORE you respond (before you even do the test analysis described above, actually):
https://www.manhattangmat.com/blog/inde ... lly-tests/http://www.manhattangmat.com/blog/index ... -the-gmat/Then come back here and tell me what you think and I can advise you further.