I'm a Muay Thai practitioner interested who has started lurking in these forums precisely because I have found that western Boxing has much more to offer in the way of articulated tactics and strategy than western Muay Thai. Personally, my hands are pretty crappy, I rely on me legs and clinchwork.

If I were to pick an art for self-defense though, it would be Judo for the ability to put assailants on the ground quickly while remaining upright. A hard throw onto an everday surface will probably be enough to take the aggression out of many unarmed attackers.

BJJ is good to know supposing you do end up on the ground, but in a self-defense situation that is probably not where one wants to be.

Boxing is probably great for SD in terms of evading wild blows, and the ability to land body shots, but throwing bare fists to someone elses face is a good way to injure your hands.