I was born in 1971, so was not really aware of stuff at the time (except my old sister had a disco compilation called "Hot Nights, City Lights" with "brick house", "I will survive" etc on it that I rocked out to when I was like 6 years old!)
...based on my records collection, however I wish you could split the difference. it seems like 1968-1972 was the epitome of soulful (leaving behind pop/twee girlie and Motown and was still pre-disco and indulgent funk/jazz/studio-jam). stuff like Leroy Horne's "don't come back" (Pompeii 1968) or Marvin L Sims "get off my back" (Revue 1969) seem to have the perfect blend of tight, focused 1960s song smithing, street-wise grittiness/attitude, and appropriate level of raw-ness in production. those are just two random examples that happen to be sitting on my decks right now, but you get the picture.
I know that answer is cheating! sorry!