It basicly a car, to move around. What's is your concern anyway ?
BMW here is overprice, not suit for light wallet.In general, Japanese engine cheaper but it can be expensive too. I used to own R32 for 8 years. RB engine not fussy as well my car now.
I drive E32 now ( I like no 32 ), I told mechanic what to change and some I do myself with help of internet.As well I can live with a lot error come out from meter cluster ! As long car doesn't stop me and save me in case of bad luck.
Just my opinion, If you have thick wallet and willing to waste your money go for original .Others again ask your wallet.
The best is try understand the car included the engine not just drive it,believe me it help a lot and will save you, regardless what engine you use. I still have 500 pages RB engine book and I also bought E32 bentley book. Great investment!