hope i can explain this premise well

which song[[s) do you thing make best use of the group? this doesn't automatically mean tons of 3 part harmonies or shared leads. But some songs really are just a lead with basic ooo's from the background. not hugely compelling examples, even if the song is a good one

some examples that come to my mind:

Come See About Me - such a classic call and response but you absolutely could not cut the lead or the bg vocals. masterful

You can't hurry love - while the bg vocals are just oooo'ing on the verses, the girls assume the role of the Mother, warning the lead that "you have to wait, you have to give and take." There's a clear role here and really adds the charm to the record

Sweet Dream Machine - gorgeous 3-part harmonies, gorgeous shared lead vocals. a very sensuous recording that spotlights each woman