Could be anything. Winner is whoever survives longest, or completes more floors, or completes all floors fastest, or kills the most MOBS on floors with near unlimited MOB generation, etc. I trust that gurw will choose whatever objective he will finds suitable for the tower he builds (if this is a competition he will do).
As an alternative to the tower, a gladiator arena in a colosseum with fight rounds instead of floors is also an option.
Copy pasta with worldedit. Have multiple towers going at the same time. Assign time blocks for players/teams to show up and fight.
Granted, if Gurw is the only proctor and a lot of people sign up, he could spend an entire weekend going through everybody.