I disagree that it's as simple as both being top notch schools. For what it's worth, I applied to GPPI but not GW -- but at the GPPI open house this weekend several of the students agreed that the core difference between the two programs is that GPPI is very quant-heavy, where GWU is very theory-based. This was not to say that one is better than the other; but you should consider what exactly you want to get out of the program, and factor those strengths into your decision.