Truthfully, it's Kanye.
Travis is in that lane comfy. A real Hypebeast rapper to the kids... Thug is in that lane kinda but he also in that Future / Gucci audience. Travis is avant garde trap with biting style vocal performances, Thug is plain ol trap with avant garde vocal performances.
This is also reflected in their output. Travis is deliberate and considered. Might drop 1 tape a year and it sticks pretty well. Thug is in that Gucci / Future lane putting out mad material, some sticking better than others.
If Thug took 6-12 months on a single album and focussed it would do bigger numbers. But doing what he's doing the quality is already pretty high imo and the numbers are accumulating.