-
probably the sram, ettix qs have had loads of trouble with the fsa rings shifting badly with di2 this season (how much of that is real or just riders jumping on a bandwagon I don't know, but presume the former) for that reason I'd go with sram
I'd honestly look into a praxis conversion bb though, I've not heard any creaking stories with them and the idea seems solid, and the front shifting will drastically be improved, if not maybe have a look into the turn zayante cranks? stiffest around and will have the next best shifting to Dura Ace rings with shimano, thanks to the praxis rings
this is food for thought:
https://fairwheelbikes.com/c/reviews-and-testing/road-bike-crank-testing/
BB30 BB though, and wouldn't want to use an adaptor. No Shimano BB30 crankset. So question is, will the Red or FSA work better with Shimano, and Di2?