Mix and match here.
Bike 1 = SRAM X9 mech and shifters, SLX cranks
Bike 2 = SLX shifters, XT mech and SRAM cranks
There isn’t much in it when it comes to shifting, SRAM shifters take a while to loosen up, but they don’t need much in the way of adjustment. My SLX shifters need regular fettling but the multi-release is a real boon too, when using my Shimano bike I tend to thumb shift when sat down and use the finger method when stood over the front end of the bike. The X9 shifters have taken a step backwards in reverting to four grubscrews to retain the shifter covers, instead of the simple chrome dial of old which I prefer.
As for the cranks, Shimano stuff is noticably better. My SLX cranks are lighter, stiffer, cheaper and easier to maintain than my Stylo 2.2 cranks. Shimano BBs are considerably longer lasting too.
[edit] Shimano chains are awful. Mine always rust at the first sign of damp within 100 miles, yet SRAM chains retain their lustre. Best bet is to use neither and go for KMC or YBN.