The MCAT is far more specific and you have to study FAR more for it. With the GRE you can study strategies and if you remember your math from HS/college you should be fine. The MCAT however requires you to KNOW a LOT of information in bio, chem, and physics. I took the GRE this year, studied for 2 weeks on and off and got 730 on quant. and 430 on verbal. I studied for 4 months solid everyday for the MCAT 2 years ago and got a 23. Best of luck if you decide to take it!!!