I have shot and owned Black Widows and Zippers.
Zipper is my choice, the craftsmanship is superb and in my hands the Zipper is the most accurate bow I have shot. The bow is absolutely dead in my hands at the shot, points great and the SXT grip is perfect in my hands. The bow draws without a hint of stacking builds up weight consistently to my anchor. Superb.
The Black Widow is a great bow too and they have different models so It's hard to compare them. I used to own a PSA and I didn't like the weight of the riser, it felt clunky heavy. I still own a PSR and that bow is my favorite Black Widow, short, light and simple. Good luck with whatever you choose, they are all great choices.
For what it's worth, Bill Dunn from Zipper is without question the best bowyer I have ever dealt with, many could learn from his customer service. You buy with complete confidence.