JT will not win this poll. To be fair though, both of them benefited from GOAT level production in their primes. Usher's easily the better vocalist and far better dancer. JT writes, produces, and plays instruments. He's even written and produced for other artists. Still, I find most of JT's writing to be elementary and at times corny, but it works.
Both of them have made music that I like, but honestly, if Timbaland and The Neptunes never produced a song for JT, I probably would never touch his music. They laced him with GOAT level beats for the majority of his career. His first three albums are remarkable. Usher had a legendary run though with My Way, 8701, and Confessions.