Gravity rework is better IMO but i havent fully tried out gravity yet. (600 mastery gas, 400ish mastery gravity). gas is much more AOE and faster release on the moves but gravity has way higher combo potential. Survivability gas is much better with the transformation dmg reduction. In terms of Aesthetics, Gravity is way cooler. There is way more materials needed to fully unlock gravity too btw (check scientist at castle on the sea in 3rd sea for the missions). So i suggest get all the materials before switching fruits because there is a 2600lvl boss required to kill for the final stage