I was born and raised in the shadow of that Marquette cross. Part of the rhetoric for keeping the cross is that it is a local tradition whereas a statue would not be in keeping with that tradition. Another argument is that Marquette "requested" that a cross be erected where he was buried. Note that Marquette's remains were removed after two years for internment at St. Ignace so nobody is buried at the site in question. I think one of the reasons why a cross was put there instead of a statue is that it was way cheaper to erect a wooden cross (it was wood when I was a kid) than it was to build a statue. Note that the existing structure is not a "crucifix", it is a naked Latin cross...two and one half stories high with its sandstone base...lighted at night.