GMAT Strategy

I know that the Kaplan CATs are known to be more difficult than GMAT prep (and I assume the actual GMAT) but my scores are waaay off.

Kaplan CAT#1 550 (Q30/V33) Sep 26
GMAT Prep #1 690 (Q48/V37) Oct 10
Kaplan CAT#2 560 (Q37/V31) Oct 24
Kaplan CAT#3 580 (Q36/V34) Oct 30
GMAT Prep #1 720 (Q48/V41) Nov 14 (This was a repeat of GMAT prep#1, but I didn't see many questions that I remembered from the first time, and those times I did I made sure to run the clock for 2min before submitting the answer)

Doesn't it seem strange that I can't crack the 600 mark with the Kaplan tests yet I do really well on GMAT Prep? Should I worry about my really low Kaplan scores or be really happy with my GMAT prep scores? I know GMAT prep is supposedly more accurate but could it be that I've just gotten lucky with the questions and that's why my scores are so high?

You should be happy with the GMATPrep scores. As you already know, kaplan scores are a bit off. Re-take GMATPrep as many times as possible. You will see many new questions.