You are correct that by population there may be fewer people over all. However, (please feel free to disagree with me -- opinions are based on my comfort levels and a single-time-experience)
I think your biggest risks are unpredicted thunderstorms, which can pop up quickly. They blow over quickly as well, but can be pretty violent in the moment. By following the north west route you'll be closer to shore and, should something come up on radar, may be able to get in close to land and put down an anchor (or, at a minimum, use the shore to keep out of the larger swells).
If you do go with the Eastern side there is something else to note: you will not be able to hug the shore as you make your way south from Mackinac to Charelvoix. There is a large shoal from the Wilderness State Park area to about 5 miles off shore. Assuming that you are trying to be as efficient as possible your route will most likely look something like this:
You could tuck into Little Traverse Bay, but at the end of the day I think it's about the same mileage). I think you'll be just as limited in potential resources on that track AND you'll have a long day further from shore -- AND, once you get south to Muskegon or Grand Haven you'll STILL have to make a 70 mile open water crossing (which will be more exposed and have equally less access to assistance should it be needed).
(Now, you could shorten that day by going to Beaver Island, depending on how long you like to run your days. But note that Beaver Island is still 18nm off of the main shore, so you will have exposure either way).
That said, that's where my comfort level lies. You ARE correct that, once you've made it to Charlevoix there are marinas/ports/inlets approximately every 40 miles on the East coast. But I think the open water exposure is a bigger risk than sticking closer to shore in a less populated area. NOT that there is anything wrong with open water trips (my spouse and I have regularly done 100 mile open water trips on Superior with out issue) -- but it is a potentially riskier venture.
IF you do choose to stick with the Michigan side the Michigan and if you want to stay in marinas the DNR has an excellent reservation system for their state marinas:
midnrreservations.com
You can register via the web or, in my experience, get the phone number and call. We were 37 feet (and a 6.5 foot draft) -- depending on the marina the website sometimes didn't have accurate info and said there were no slips that fit which, upon calling, we found out was untrue.
If you are anchoring then it's mostly a matter of finding areas with good holding in the various bays/inlets.
One other note, FWIW -- when I was planning our trip I used Google Maps (in the web browser) and the Measure Distance function in satellite mode to figure out how for between various ports of call and estimate the length of each leg. I know the chart plotter can do the same, but having the Satellite view was helpful in seeing each marina, how close they are to town, and measuring multiple legs (then using the chart plotter to see depths and really zoom in to each area.
Ok, two other notes:
I'd recommend getting a good weather radar app for your phone and watching that marine forecast site from earlier. Refresh/check regularly through the day. Watch for storm systems over land that may be tracking your way. That way you'll hopefully have time to pull down canvas and/or find a place to tuck in before any systems hit. You'll most likely have phone data for most of the trip, but regular checking through out the day is important (you're on a bigger boat, but see the other thread about the father and two kids who passed away after getting hit by an unexpected storm in the Green Bay area last weekend).
Sorry if I'm getting too wordy here, but hopefully some of this is helpful.
Doug
