Southern Soul types (both fans and industry people) always enjoy taking the same shot at their Motown rivals, arguing that Detroit's finest acts had been polished up and watered down for the benefit of a white audience. In other words: there's no authentic soul in Hitsville, USA.
Certainly most Motown acts don't have the raw dynamism of the early Stax years, but I don't think that makes them a bunch of sell-out hacks as some people like to suggest. Case in point: the Marvelettes. With their unvarnished vocals and (slightly) edgier subject matter (compare the Supremes' "Baby Love" with the Marvelettes' "Don't Mess With Bill"), they've always managed to bring a ragged touch to that polished Motown sound. They're my favourite girl group, and I'd put them up against Carla Thomas any day. Here's "Too Many Fish in the Sea":