As a pilot your main priority is a chain that has lots of locations. 24 Hour Fitness has a LOT of clubs in the western US, many of them convenient on pilot layovers. They have a lot of really nice, new clubs. There's one in the LAS airport that I use on longer sits. They also have the standard reciprocal agreement with many other clubs.
They have the distasteful salesman thing going, but once you get past that, for $30/month it's pretty convenient. I wouldn't pay more than $100 initiation. Get the Sport Club membership.