At least for me..........I'm all about the spot at 13 mile.
Last year was great, but there is so much less traffic down there. This may change because the cruise is supposed to expand down into detroit. maybe a short list will help everyone.
Zion church lot pros : better bathrooms, easier to enjoy a liquid bread beverage, less people clamoring over the cars.
Zion church lot cons: less to see, longer drive / walk to get to more action, a little off woodward (behind a building) so not as much exposure.
13/woodward lot pros: Really is the center of the cruise, much more to see and do, wayyyyyy more crowded, much better exposure for our cars, and this last one is a little more of a personal opinion...this is where I've gone pretty much every year for the past 12 years or so.
13/woodward lot cons: Port-a-potties on one side of the lot, it really is more crowded, depending on what part of the lot we're in people might think we're a part of the Chrysler display and try to look in our cars a little more than I think most of us would like (think auto show). Since this is also a public lot, and where the police have a staging area, it's up to you on whether you want to have a "barley pop" or not

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Just a few quick thoughts.......feel free to add any others.