My thoughts on this and just did it to my car about to turn 60k. I choose BMW parts and will go into why for each level of expense.
Least expense: Amazon Bosch plugs and
Coils is very affordable together
https://www.amazon.com/dp/B0774YC95J
- I have read reviews on ECS, Turner and Amazon it appears 1/10-1/20 fail rate on this combo the reviews are like a broken record. $140ish
DIY Recommended: Find your fav supplier get
Delphi Coils($40per) and
NGK plugs This is oem but without the BMW payment plan. fail rate is low, cost $320ish
BMW Parts: it's about $575 for the BMW parts one advantage is BMW covers them for 2years parts and labor even if a dealership didn't install them. I work at a BMW dealer and got a discount but still lots more for the middle option. peace of mind won the day on the 2yr coverage.