note: i'm almost 100% positive the 13mm belt is intended for larger men whose midsections already have some "give" to it. i have a 13mm and it's almost oppressively stiff. if i hadn't dropped $100 on it (lever belt) i'd be tempted to switch 'er out for a 10mm model that's more flexible.
haha. I 've always thought the exact opposite. I've got an inzer double prong 13mm that I got stuck in one time. I was squatting heavy and my training partner cranked it down on me. After my set, we couldn't get it off. I kinda had a mild comeapart, which didn't help. It took several minutes a couple of other guys to get it off. Because of this, I also only use single prong belts anymore. The worst feeling in the world is finishing a max squat, not being able to breath, and then not being able to get the belt off so you can breath.
I personally like the belts that are sort of in between --ie a "thick" 10 mm belt is probably the best description.
The biggest issue with a belt isn't how they perform when they are new, but how they are over time. Cheaper belts tend to warp and the threads seem more likely to come apart. I've gotten the best use from the one I purchased from Elitefts. That belt is 2 years old now and really is pretty much bulletproof so far. No thread wear, no peeling of seams, buckle is still in great shape and isn't loose.
I've got an old Adair, which i've had for almost 5 years of pretty hars handling (I'd keep in on the back of or in my truck in the sun, used it for pulling the sled, etc). It finally started to crack up near the hole I use the most and the end. Personally, I think that was pretty good wear for a low cost belt.
Inzer belts seem to want to stiffen up if you use them, get them really sweaty and then don't use them for a couple of weeks. I dont' know enough about leather working to know why that happens, but is seems to be the case for every inzer belt I've ever had. The key is to hang it upafter your workout, don't keep it rolled in a gym bag. That said, Inzer belts are good quality. My wife has used hers for several years and its still good.
I've never used an APT belt. I hear they are good quality, but I don't know from use.