I used to wear the rubber belt, but I'm pretty skinny and I found it tended to ride up my waist, which after a quarter or two rendered it useless (I constantly had to push my shirt in on-court to keep it from coming out).
So I switched to the shirt-stays, and considering that I am in the military, I'm surprised I didn't think of that sooner. They rub on your legs a bit, but that's not something you notice until after the game, and after a few weeks your skin gets used to it. They are AWESOME for keeping the shirt smooth and crisp looking.
One obvious downfall: they don't work in the summer. Shirt stays and shorts are not a good mix when you're trying to get a job at a camp.
