Basically (without getting into the benefits side of the equation) the MR points earning structure comparison is:
Gold - 4x MR points on restaurants and grocery stores. 3x MR points on flights booked directly with the airlines or on AMEXtravel.com. 1x MR points for everything else.
Plat - 5x MR points on flights booked directly with the airlines or with AMEX travel. 5x MR points on hotels booked with AMEX travel. 1x MR points for everything else.