retro, don't really know as I only ever used Shimano
modern, I use shimano XT cassettes, 'cos they're lighter than the equivalent Sram offering & don't cause burring on my Hope ProII freehub body.
I run Sram X9 shifters & rear mech's as they're less prone to having shifting issues due to gunky cables & they have a more positive feel to the shifts
Front mech is a Shimano XT, as it shifts better than the Sram ones
Sram chains are better than Shimano chains, but I now use KMC chains as I feel they're better value & last just as long as Sram chains.