There's still hidden unpublished benefits that come with GO, just depends on if you care about it or not.
I found that as a GO on long haul J, I get served my meals first. The flight crew also remember you by name and address you by name even in PEY and Y I've found. These are nice little touches I've found that add to the service. Anecdotally though I'd say I get more op-ups as SL than GO. I've been upgraded 0 times since becoming GO. As SL, I used to get upgraded about 25-30% of the time with the same travel pattern.