Chase McGuire said:
Maybe it's because I'm young, but I feel like Nolan should be running away with this.
Your youth isn't keeping you from seeing some of Scott's earlier works like Alien, Blade Runner, or some that are not included in this tourney, like The Duellists or Black Rain.
My own vote went narrowly to Nolan, who I have yet to see a bad movie from. If I was to put a list of what I consider the best science fiction movies ever made, both these directors would contribute to them with Alien, Blade Runner, Interstellar, and Blade Runner 2049 (Scott produced). The Dark Knight trilogy, along with The Prestige, Memento, Dunkirk, and Inception give Nolan an edge.
As opposed to Scott, who has made some clunkers - American Gangster, for instance. I really enjoyed Prometheus, and am likely one of maybe a dozen people on planet Earth that enjoyed Alien Covenant (liked it better than, say, Alien Resurrection); I really like the character of David, introduced in Prometheus, and his introduction in the opening scene of Alien Covenant with his creator, Weyland, was probably the best sequence in the movie.