I dont know for sure in dyno numbers, but when i ditched my stock o ring chain and bought a standard it was a noticible power increase. If i am correct i saw a dyno sheet a few years back that claimed about 1 horsepower between the 2 on a 350X.
Thats a noticible jump in my book. Then again it depends on the chain. I buy cheap primary drive H racing chains. They usually last about a year, but the tensile rating is 1000lbs higher than any oring chain under 80 bucks, not to mention the thing still looks like new when its worn out, so most of the time you can take a couple links out and ride it for a lot longer. Its kinda weird, after the first ride the chain will stretch quite a bit, then after than first ride the chain stays at the same adjustment for a long time, sometimes 3-4 rides.
Idk i just cant see spending all that money on a chain with orings in it, knowing that they dont really do anything for me since i avoid water and mud plus keep my chains lubed heavy. But honestly as much as a chain moves around and the rollers spin, how much water do those orings really keep out? My stock chain didnt last as long as those 520 H racing chains, and it sure did make a shitload more noise, it also started to litterally fall apart before it was out of adjustment, the rollers and orings were falling out on a regular basis, and i lubed that thing every ride. I believe they use DID stock dont they?
When it comes to chains and sprockets i have found that you are actually better off saving your money and buying the cheaper stuff, cheap sprockets last just as long if you just keep the chain adjusted right, and the midgrade chains usually last over a year.
Then again this is only my opinion, most of you guys hit alot more water than i do, i stay clear of mud and water when possible. For some reason to me, just one time out mud riding completely ruins the feel of my quad for weeks, it just makes everything feel weird and like the entire machine is worn out untill i get used to it again. This is also most likely why the only bearings i cant seem to keep in the thing are swingarm bearings, other than that ive only replaced one wheel bearing and only because it was a little loose.