[Luxury]

I could not and would not say that it is better. I have zero experience with either. (Can of worms) I don’t think there was always other options for the DCT’s because of the drive ratio.
Quaife would be my choice though because I trust Dinan. While they would not, extremely unfortunately and disappointingly, confirm Quaife to be the insides of their former product; my research gives me confidence that it was and that Quaife has a good product. The two brands on my car are Genuine BMW and Dinan. I will keep it that way, even if it means no LSD for me.

I’m not confident, but I have the assumption that the manufacturers do not touch the case or car. I assume third parties will either assemble the LSD and case (precision work that should be carefully considered) or install the assembly (any mechanic shop, I suppose?) or both! It’s possible to order a case already put together with or without sending yours in. It is your decision to pay for a core or not.