My engine builder has had great success with Pro Comp heads. He also like you have used lots of the name brand heads too. Just depends on customers budget and what they are after. I know a few guy's that have purchased the assembled version and have no problems. I have a bud that had problems with new out of the box Dart heads, even with replacement pr, so he will never touch another pr. No matter what Co it is, crap gets out sometimes. I purchased a new Comp Cam that was ground wrong,..sent it back Comp, they verified it and replaced cam and my gaskets. My Pro Comp heads are still in the box...I hope I don't have problems...LOL..I purchased them bare.