This will become the "Wallenstein vs. Bro-Tek" issue. Because the Bro-Tek is more 'linear', it doesn't look like it will have the same torsional stresses as the Wallenstein unit will have. I believe for this reason the Bro-Tek unit is a bit more structurally more sound and probably capable of handling more "brute force" (picking up an irregular rock, for example) without folding or deforming.
For every up, there is a down. The Wallenstein unit looks SO MEAN and heavy. And the wider, more "engaging" grip would make better suited to timber and brush. My fear with the Wallenstein unit is if you grip too hard on one side of the teeth and invoke a huge torsional stress, that it will deform.
I certainly hope not, though. I have purchased a Wallenstein thumb for my Woods BH6000. It just looks so pretty. Should have the thumb on Monday and my dealer should be picking my tractor up for the BH installation next week. When I get it all back, I will be eager to evaluate.
And, of course, post pictures.