One thing worth mentioning when comparing Shimano and SRAM mechanical, is that Shimano uses barely enough cable pull (IMO, not really enough since 9s), so on Shimano bikes the cable system has to have a rather good signal to noise ratio in order to work properly. SRAM uses significantly more cable pull, which translates to more cable friction felt at the lever and a bigger throw to make a shift, but the indexing is far more tolerant of friction and mush. Also, barrel adjustments are a lot finer.