Just kidding, there is no definitive answer
First a little house keeping. I'm no chaos, and I'm certainly no blowback, I'm just a guy with a couple of AR 9s, a little free time, and some 9mm ammo.
I don't have any sophisticated electronic measuring devices, or any unsophisticated electronic measuring devices for that matter.
The ammo I used is my standard 9mm PCC load. It's a 124gr jacketed RMR bullet in front of 3.8gr of 231. Out of a 16" barrel it's going 1140fps giving a power factor of 140.
The test guns were both 16" barrels that I shoot in PCC in USPSA.
The first one is a Juggernaut Tactical AR9 with a Scheel Roller Delayed Blowback buffer. The buffer has little rollers that "lock" into little windows in the buffer tube. The amount of "lock" is controlled by little springs in the buffer that push out on the rollers. It's adjustable via spring change.
The second one is an Aero build with a CMMG RDB Radial Delayed Blowback barrel and bolt carrier. It has lugs on the bolt like an AR15, and matching lugs on the barrel. It's non adjustable.
Both of them try to accomplish the same thing, keep the gun in battery longer.
The tests were:
1. The Juggernaut with the Scheel Roller Delayed Blowback buffer
2. The CMMG RDB Radial Delayed Blowback, with a 3oz buffer
3. The CMMG RDB Radial Delayed Blowback with a 1 oz buffer
4. The CMMG RDB Radial Delayed Blowback with a 6oz hydraulic buffer
The results
The Juggernaut with the Scheel Roller Delayed Blowback buffer is very soft. Next to no for bounce, in fact the dot just wiggled to the right.
The CMMG RDB Radial Delayed Blowback, with a 3oz buffer, is "sharp" with much more recoil and dot bounce
The CMMG RDB Radial Delayed Blowback with a 1 oz buffer is MUCH softer than the 3oz buffer. Much softer. Not quite as soft as the Scheel, but pretty close.
The CMMG RDB Radial Delayed Blowback with a 6oz hydraulic buffer is the softest of them all. It's like shooting a .22. No bounce, no recoil.
I'm waiting on my dual weights and flat spring from Midway so I can build blowback's “Gentle Recoil” 9mm AR Project.
Questions? Answers? Anybody want to buy me lunch?