Robb is correct, Allem does NOT make a roller release for the Blaser. I had them install the double release back in Jan in my Blaser & thus far very happy with it. I know guys that have had McCarthy's & are also very happy. From what I understand, a bit quicker turn around with McCarthy's. For Allem's, I e-mailed & "made a reservation" for mine. When they were ready for it, I got a call from them. Shipped the reciever down & had it back in about a week or 10 days. I think I made my reservation in early or mid November. To answer your question, I am not sure if 1 is that much better than the other.
I have had Allem's roller releases in other guns, and they are as good as it gets (but as already pointed out, they are not available for the Blaser). I wanted to have Allems do my Blaser but the wait time then was SEVERAL months. After I talked with a few sources I decided to Have Pat McCarthy do the releases. Pat was exceptional to work with and his releases are as fine as any I have ever tried. They are also adjustable. Pat even followed up with a phone call to me about a week after he shipped them just to be sure everything was alright.If I were to buy another Blaser, Pat would be my first call.