Sarah Vaughan was certainly the most skilled singer of all the famous ones. She had a ludicrous good technique and a range that made most competitors fade away. Although, I could imagine that for many listeners she was always singing way too eclectic. She always wanted to push her limits, wich for listeners sometimes can be too much to bare. The good stuff, if you can grab what she does - singing-wise - is just stratospheric amazing! Really unsurpassed until this day.
During her long career she made many different things. The early stuff is very interesting, since it is so undocumented.
Here are some transcription of her orchestral-recordings.