It's not easy. I love so many of the different singers that have been mentioned. In the end I looked at my record collection and did some counting. The great Big Joe Turner came out top - I have 23 of his LPs and 11 CDs, plus a few cassettes.
Over 45 years plus of recording, he covered classic blues, rhythm & blues and jazz and was comfortable in all contexts.
I was lucky enough to meet him after he had just done a sound-check for one of the blues package shows at the Royal Albert Hall in the late 1960s.   He was complaining of a sore throat. The only remedy i knew of in those days was Meggozones, so I dashed down to a chemist in Kensington High Street and bought a tin. Upon receipt of the lozenges he opened the lid and poured over half the contents down his throat.
I was worried that this could do some serious damage, but he sang like a dream at the evening concert.