I think everyone gets same price now since bankruptcy if an employee uses gms for purchase dealer gets more money from gm in the deal. That the way I understand it! More profit for dealer in sale of vehicle.So you should get same deal either way.
GMS deal is an extra rebate dealer can apply for, for qualified people and immediate familty, GMS deals are great the price is set, (usually below invoice) plus the extra rebate, plus any other incentives available at time of purchase. if you qualify for one of these deals your pretty much protected, GM frowns on any monkey business like trading these numbers, and they are scrutinized, dealer can get in trouble if they break the rules.