...used both and have since preferred to use the clamp type. Reason: Better gas journal seal with clamp type. Barrel gas journals will differ in OD dimensions just as gas blocks will differ in ID dimensions. The clamp type can accommodate those differences better, providing a better seal from the get go. Caveat: Gas leakage will eventually accumulate and build up into a seal with set screw type as well, but it can be disconcerting when you see that initial leakage evident on a new assembly. When you have minimal effort required (loose fitting) when you slip the gas block over the barrel gas journal, that indicates a dimension mismatch. As you tighten the set screws the gas block upper section is "pulled down" for a closer fit, but the lower half is "pulled away" and increases the gap between the outer portion of the gas journal and the inner portion of the gas block.