IMDB is reviewed by the general audience while Rotten Tomatoes is reviewed by movie critics ( they also have Audience reviews).
You should also include Metacritic, they aggregate reviews from different sources.
Parehas lang naman sila, kasi kahit gaano kataas review nila eh kung di mo talaga trip yung movie. Depende talaga sa tao kapag napanood na yung movie/tv series.