I run almost exclusively Oregon chain primarily because of price and performance. I spin my own chain and go through about 100' per year. I run 3/8 .063 chisel/chisel in all three configurations- full comp for my personal firewood (oak), semi skip on 32" bars and by far my most popular, full skip for 36" and longer bars. I grind on a Silvey SDM-4 for the bits and an HDG-6 for the rakers and gullets. I've noticed no difference in the bit hardness over the years but but several of us old geezers have noticed in the last couple years that the chain doesn't seem to stretch as much as it used to. This is not due to higher quality B+C oil as we're running a lower quality (and priced) oil these days. They just seem to be manufacturing it better.
The angles on the "C" series chains have changed over the years though as I have some chains from the 80's for really long bars (50"+) that I hardly ever use anymore and the difference is quite visible even with the naked eye.
I will say this. Stihl chain bits are definitely harder than Oregon. This is noticeable even on a grinder. Occasionally when I buy a new saw I will get it with the stock Stihl chain and I can feel the difference in hardness.
In an earlier post someone mentioned that some Oregon chain is being manufactured in China. Many people are unaware of this but it is a national symbol of pride in China to make a product of the lowest quality possible and still get the people of another nation to buy it. This is particularly true for the people of the United States. I say this in jest but it would not surprise me at all if this were true. What a bunch of crap! If I continue it will have to be over in the political section of the website. LOL
If you're having issues with your Oregon chain definitely get ahold of your distributor as It has been my finding that corporate Oregon really does care. Years ago they actually sent a rep out in the woods to get our feedback and we got a bunch of freebies to boot. I've been told (but can't prove it) that most unbranded chain is Carlton. I always thought Carlton made a good product but have limited experience with it and even that was decades ago.