For me, my favorite, range, tone, improv ability which is bottomless and sheer listenability, Sarah Vaughn. Can't argue with any of the above, love Ella too for many of the same reasons as Sarah but less to degree, Sarah was a true genius both vocally and artistically. Not familiar with Jane Fielding but will surely check her out! And Eva Cassity died much too young. Not to forget Dinah Washington, amazing songstress who also left us too soon.