The only good reason I would see (personally) to travel up the WI side would be if you had some specific sights in mind to stop at along the way. For example, if you wanted to stay a night or two in the Door County peninsula.
The western shores tend to be sandy beaches (MI side of L. Mich.) and the eastern shores, I believe, tend to be more stony. Not sure if that will matter to you, just thought I'd mention it.
When at Sleeping Bear area, if you'd like to swim, just north of Empire take Voice Rd west to Bar Lake Rd, and north to the N. Bar Lake. This nice little lake is separated from L. Michigan by a sand bar and is much warmer than the big lake, but you can walk just a little ways (maybe 50 yards?) and be at the big lake too.
In Mackinaw City, at the dead end by the dock entrance, walk north (left) a half-block to the local bakery. Great pecan rolls and the best homestyle cinnamon bread I've eaten (outside of my sister's kitchen). Mackinac Island is a great place to ride a bike all the way around the island (no cars, nice water views), so take bikes if you have 'em or plan to rent some on the island.
If you get as far west as Manistique, the Big Spring at Palms Book SP is worth a visit. Blue-green water so clear you can easily see the fish at the bottom, 40' below. That plus historic Fayette SP would make a nice little day trip.
