I'm currently a member at 24-Hour Fitness, and miserable. I was a member of Gold's Gym for 7 years, but switched after moving to the other side of town. One of the biggest mistakes I've ever made in my life.
Gold's constantly and consistently adds capacity to meet growing membership size. They also stock the latest and most modern equipment available. Finally, they have knowledgeable staff, as opposed to 24-Hour Fitness sales people who are overweight and have no idea what fitness is.
Pros: New Equipment, Cardio Annex, Knowledgeable Staff
Cons: Small Locker Rooms, No Parking 6-8pm