The better question would be G-League vs. college. Honestly, looking at someone like Trae Young, I don't think the college route is going away any time soon. Trae went from a fringe first rounder, if that, to the lottery because he was killing it at Oklahoma on tv every week. If a player plays really well in the G-League, yet nobody outside of very hardcore people notice, would he really shoot up the draft boards the same way? Basically, I think playing on a big college stage with millions watching on tv is still a route most will choose to take.
And I never think that one year of college really "prepares" you for the league all that well. But, you are judged against your draft peers more often in college than overseas or in the G-League, thus scouts have a better way to judge your talent against them.