As an example, on Michigan Ave here in Chicago, you can visit a Banana Republic store inside Water Tower Place, or you can walk two blocks down Michigan to visit a Banana Republic store on the street. While the stores are very close to each other, they attract different shoppers (the Water Tower Place would get more tourists while the store on the street pulls in more locals). Probably CF is looking at the same situation with MA: while there's some overlap, the parks target different segments of the market. CP is positioning itself as a resort, a destination for a multi-day trip, while MA is a one-day park; MA is a more local park than CP with the vast majority of patrons (outside of coaster enthusiasts) coming from within the state.
Too, MA markets further north into Michigan than CP, and I'd guess is more active in Southwestern Michigan, too.
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Time flies like an arrow.
Fruit flies like a banana.
--Groucho Marx