South Jersey to Traverse City, MI

I did the drive from NJ to WI a few times a year for 3 years while in grad school. I never encountered a reasonable option other than I-80 or I-76. Those who have done it more recently might be able to say more definitively, but my sense is that the turnpike will be a bit flatter (some tunnels lessen the vertical climb needed to traverse the mountains), and you have the advantage of easy on/off service plazas at fairly regular intervals along the way. On the flip side, I-80 would save you the tolls until you meet up with the Ohio Turnpike. In August, weather will not be the concern as it would in the winter.

I'd spend the money and stick to the turnpike from south Jersey, but that's just me.