It’s the 1:1 actuation ratio of SRAM that makes it shift better than Shimano that still uses 2:1. In lamens terms what that means is that for each mm of cable movement on a SRAM equipped bike the rear mech will move an equal amount of mm’s, where as a Shimano equipped bikes rear mech will move 2mm for every mm of cable movement.
The 2:1 cable actuation ratio was developed in the dark midst of time for road bikes with down tube shifters. It was done so the rider could shift through all the gears on the down tube shifter without the shifter having to move more than 90 degrees from the lowest to the highest gear.
All though I use SRAM on my bikes the technology (apart from 1:1) and build quality is superior within Shimano groupsets when compared to SRAM. It’s just that 1:1 makes such a difference in shifting quality, especially in the muck, that SRAM gets the nod from me.