weight belt????

Thera are al sorts of rubber belts. Some are thicker than others.
I use two sets of rubber belts. One somewhat thin loaded with 3-4kg and the other one is thicker, with more weight on it. This way neither one is taking more abuse than it can handle and they last a long time. As for the buckle, if the plastic one is well built , go for it.
Anyway it is better to change your belt once in while (which you won't) than having one that would last for ages but every time you dive you end up wearing it round your armpits.
Even though there are some ways gettin round this problem they involve some more belts or ropes and buckles and staff like that which I hate.

Another advantage of a rubber wieghtbelt is that it lets you take deep breaths more easily by not putting an inelastic constriction round your waist - put your hand just below your belly button and take deep breath...
No spearo worth his salt will use a webbing belt (unless he has the harness type but thats another story!)