It's a loaf of bread. Yes, I don't want to see "Made in China" on my parts, but a German made aftermarket is certainly good enough for me. In my experience, with engines/heads, if you have problems after a rebuild, 9/10 times poor workmanship is the problem and not inferior parts.

Oil seals have been the only aftermarket engine part to give me trouble. As in, 9 work great and number 10 is lopsided. That, and things get mislabeled.

Anyway, being OEM does not mean you magically don't have these problems. I have a big box of OEM BMW parts that are factory mislabeled.