All three locations are solid. Addison is the "mothership." McKinney is second busiest and RBD is the slowest (read: aircraft and instructors more available). You will burn a lot of Hobbs in ADS getting in and out, though. Something to consider.
RBD probably has the best "flight" location and it's quick to get in and out to the practice area and utilize the Southern DFW approach buffett of not only RBD, but also HQZ, JWY, GPM, and GKY.
Good MX, good instructors, and nice diversity of aircraft. Not the cheapest in the DFW area, but you do get what you pay for. Owned by retired Delta CA and operated by his son, an AA pilot.