I agree with Braveheart. I don't think any currently made two blade, COC, glue on broadheads are "bad." However, some that were made in the past can be real "dogs". I remember one brand that had an nylon or plastic ferrel with a long, pointy blade. Heck, you could bend it in your hand!
Pavan made a good point about the Zwickey Deltas. (A great broadhead by the way) If your tune isn't good and/or you have a bad release on a windy day, they may plane on you. That can be said for ANY wide, solid, two blade head. Ace standards are tough, easy to sharpen and come in a wide range of weights, but some folks say they are "picky" about getting a good fit with certain broadhead adapters. I have nothing but great things to say about Ace. I have read that some folks have had Magnus II broadheads bend on bone hits when they left a needle point on them. I have found that the Magnus II is one of the easiest to sharpen. I have read that some folks have had Zwickey Eskimos bend on bone hits when they left a needle point on them too. The Eskimo has also taken every game animal in the world and is "the standard" two blade glue on broadhead. I bent the blade and cracked the aluminum ferrel on a Howard Hill broadhead once when I was trying to "work it" out of a sweet gum tree. They also fly as good as a field point and Howard Hill seemed to have pretty good luck with them. If you like single bevels, the Grizzly comes in a wide range of weights and has a large, loyal following. The best way is to try them out for yourself and see which one you like the best. Some folk (like me) aren't able to pick just one!