I know there's a Shimano and SRAM version. What I don't know is what's the difference between the Shimano versions?
I am resurrecting this old thread to give what I think is a solid answer. If I understand the question, it's about the product hierarchy of SRAM's Shimano-compatible 2:1 grip shifters.
From the SRAM spare parts catalog:
http://cdn.sram.com/cdn/farfuture/x2...pc_rev_c_0.pdf
pg. 44: SRAM X.0 / SRAM X.9 / SRAM X.7 / ROCKET /
ATTACK - TWIST SHIFTER (2005-2011) 3x9
pg. 45: 5.0 /
CENTERA - TWIST SHIFTER 3x9
pg. 46: 3.0 COMP / 3.0 /
MRX COMP / MRX - TWIST SHIFTER 3x9
So, Attack is somewhere near the upper-end products, Centera is similar to 5.0, and MRX Comp is similar to 3.0