Personal experience of MTB kit Dave.
cassettes don't shift very well, or last as long as Shimano
Chains are chains are chains, but Sram are noisy and don't last as long before stretching
Shifters and dérailleurs may shift slightly better due to different cable pull ratio, but gripshift has no place on any bike.
Have you seen the price of Sram?
I don't expect everyone to agree, but if i was recommending products, I can think of many different manufacturers to suggest before scam. Shimano, Campag, KMC spring to mind