i used to have elite rings. i'm not sure if they were I or II, but i got them in august 2007, so whatever was around then was what i got. they were great, no complaints. then one day somebody broke into my car and stole a bag containing those rings, some vibram five fingers, and a homemade clubbell. since then i acquired some xtreme rings (the coach sommer ones) from another regular member on this site.
3 major differences have been noticed
1. the elite rings have a knotch in the handle that the strap slips through. the extreme rings don't have the knotch, so you loop it through the big hole in the rings. in retrospect, i guess i could have looped the strap through the big hole in the elite rings as well, but it never dawned on me. anyways looping the strap through the big hole allows you to take the straps fully out of the rings and pack them up more easily. on the other hand, when the strap goes through the big hole, the ring well tend to rotate when you grab the handle so that your hand is on the bottom and the strap is on the top. you may say "well why would you grab it any other way?" when you're initially working on muscle ups, it's helpful to grab high up on the thumb side of the handle, so that the pinky/hammer end of you wrist is able to push down on the ring. this make the false grip pull up easier to manage. this is less necessary as you get stronger. i just got out of shoulder rehab and had to relearn muscle-ups, so this sucked in the beginning since i couldn't maintain this different grip. i'm back to gripping the bottom of the ring again, but i have to kip the muscle up right now.
2. the xtreme rings have a bumpy, gritty handle that should aid in grip, but the material overall seems to be more slippery than the extreme rings. i had to put grip tape on the xtreme rings for a stable grip, especially if even a moderate bit of sweat was on my hands. a roll of grip tape is just like $2-3, so that's not a big deal.
3. ok this is my main frustration. i don't ever recall the straps in my elite rings slipping in the metal clamps. they felt solid. my xtreme rings tend to slip even if i'm holding statics, like just a support. in statics though, it's no much more than a centimeter or 2, but that's noticeable when you're in a support. if i start doing pullups or what not, things become aggravating. thus i mostly have to limit my ring motions to very controlled, slower motions. if need be, i will loope the slack end of the strap around the high bar and tie it off on another pole. this way there's no slack for the clamp to slide on. i can actually do basket swings and what not in this state without any sliding. the problem is that they are not as quickly adjustable in this state, so switching between like muscle up heights and ring handstand heights (i'm still doing these low on the ground) is not fast.
i think the reason that they slip is because the xtreme rings have some sort of paint coating on the clamps that may make them slicker. it may make them look better because they're all black, but i'd rather have a sturdy, no slipping clamp.
aside from those points, i will mention that the xtreme ring handles do feel more solid than the elite rings. i did worry about my elite rings cracking at times. they never did, but they felt a bit too hollow sometimes. the xtreme rings feel very sturdy, and i am not afraid of them cracking at all.