The Hill will act as a tie-breaker in terms of the amount of meeple. So having the Big Meeple on the hill does not break the tie if there is one.
So if both have the same overall strength of meeples, and both 1 meeple (whichever sort) on a hill; it remains a tie and they both score
If you have 1 feature with multiple hills, it doesn't change the outcome.
If both have the same strength of meeples, and both at least one on a hill; it stays a tie.
(See also
here and more specifically on footnote 4