The "which grapple" debate is about as rich and entertaining as the "JD vs Kubota" debate. Lots of posts/threads here and elsewhere on this.
If you're going to uproot trees and dig out rocks, you want something that is stout enough to not fold up into a pretzel. Both Anbo and Bradco make really really heavy duty grapples with steel up to 1" thick. But they're heavy, so you lose more of your lift capacity and you get a more unsteady feeling carrying stuff around in your grapple.
If you're going to move brush piles and stuff you might want to go with a light duty grapple. Not only do they give you more net lift capacity but they are cheaper.
I think you'll also find the more expensive units are welded up from abrasion resistant steel plate (kind of like your loader and box scraper). Whether this is important or not depends on how you will use the grapple, but it does add considerably to the cost of the unit.
Finally, there have been some good arguments (mostly put forward cogently by IslandTractor) that a narrower grapple is preferable to a wider grapple. Obviously a narrower one is cheaper and lighter than a wider one, all things being equal.
Finally, there was one big grapple fabricator in North or south Carolina (can't remember which) that spawned a bunch of clones as employees set up shop on their own. So this leaves a lot of choices of manufacturers, who often make what appear to be identical units. And, of course, the Chinese are now involved making really cheap ones (but not necessarily bad ones).
HTH.