In my experience, the ammo belts that I've bought have all had rather tight ammo loops when new. "Rather tight" meaning that when first inserted, the cartridge case actualy had to stretch the loop before it would fit.
That has been true for Hunter and Bianchi belts....don't know about the others.
So, just going from that.....If I was buying a new belt sight-unseen, I'd get the 44/45 version.
Hope this helps.
DGW