As a newly minted GS, I am not expecting anything more than when I am a 1K.
Based on my readings of the posts in this forum, I feel the GS benefits are just slightly marginal than 1K's. My upgrade from Y to F/C for C to F have been cleared almost 99% of the time when I was a 1K. GS and 1K board together, and I don't travel on awards tickets to enjoy the upgrades.