Assuming both fighters are fit, in nick, and 'on it', and that there is meaning to the fight (eg belts on the line) then Fury would win, probably by a stoppage.
Fury would be bigger, heavier, stronger, and I don't think that Lewis outboxes him; he certainly wouldn't out punch him, nor punch him out - we have seen Fury take punches from hell from the hardest puncher in world boxing, and come back, and Lewis, as a puncher, does not compare. Fury has stopped Wilder, a 'big' heavyweight, twice.
I also think that Fury has more 'edge': if Lewis was a fitba' team, it would win games, but would consistently fail to convert its superiority into the number of goals that it ought to run up.