I would guess that for most flights on this route, ATL is worst followed by MSP then DTW.

Part of my reasoning is based on the different ratios of FC seats to total seats on various aircraft types.

On the ATL routes, the 777 has great seats and a decent ratio, but I suspect that it attracts elites (including SDC directly into FC) for this reason, although if it now costs more (in money or miles) to upgrade these flights, that could make it less bad. Otherwise, the ATL nonstop is a long flight, but there are some aircraft being used with favorable ratios. MSP generally has very unfavorable ratios and it's an elite heavy route, even for MSP.