I had the same problem with Zwickey's, separating at the welds. I know thousands of people swear by them. However, every time I look at one my mind goes back 25 years back and I see six new heads with failed welds. Therefore, I have zero confidence in Zwickey's and will not use them.
I have never had a failure with a glue on Eclipse (haven't tried their WareWolf?), Grizzly, or VPA. The 145 grain Eclipse with bleeders is my prefered head, but I do have a couple of the new Instinct's in the quiver this year that I'd rate on par with the VPA.