tw369 - It also depends on what type of diving that you want to do. If you are looking for great wrecks within reasonable limits, Mackinac is beautiful. If you're looking for something on the deep side, Milwaukee offers some incredible wrecks (Walter B. Allen, etc.). If visibility is a concern, the Green Bay can change on a daily basis (some days excellent, others less than a foot) - the further north you go, the worse this seems to get. If you've never been wreck diving in the Great Lakes, it's a real treat. I hope you guys really enjoy yourselves.
The books are an excellent resource.....