My experience with Remington's managed-recoil sluggers was similar to PHATINJUN's. Their point of impact at 50 yards was only slightly lower than the regular sluggers. Since I was using them in my old Remington 11-48 (smooth-bore, bead-sight), the change in POI was insignificant, and I didn't "aim" any differently with them. Recoil was noticeably lighter, but I wouldn't know how to put a number on it. Unfortunately, they were less accurate than the regular sluggers. That gun will put the regulars in a 4" ring at 50 yards, whereas the managed recoil sluggers shot a 7" group. Federal's low-recoil TruBalls were even worse. The only low-recoil slug that equaled the performance of regular sluggers out of that gun was the Brenneke THD, which typically produced 3" groups. That gun could take deer at 50 yards, but I never trusted it much beyond 50. Somewhere between 50 and 70 yards the groups opened up severely, so that I couldn't confine them to an 8 1/2 by 11 sheet of target paper. I speculated that at some point beyond 50 yards the slugs began to tumble and fly erratically. I've since switched to a 44 magnum handirifle (legal in Indiana) and can confidently take shots out to 100 yards.
Regarding the relative recoil of 20 gauge slugs, don't disregard the influence of gun weight. Many 20 ga guns are lighter than their 12 ga counterparts, and that can make a big difference. My very first shotgun as a kid was a 20ga break-open Stevens single shot. I loved that gun for its "light weight and light recoil". I never took a deer with that gun, but I shot a lot of slugs through it intending to. Later, when I inherited my dad's 12 ga 11-48 semiauto, I was shocked at how mild its recoil was compared to my old 20 ga single shot. I realized that I had spent my youth pounding myself silly with that "light shooter". I often think about that when recommending shotguns for beginning shooters. I think a semiauto with a youth stock is the way to go.
Duane