Both, I taught band for 37 yrs. and reading scores is second nature.
Playing jazz, hardly ever used a chart.
Since retiring I am sure my note reading has diminished from lack of use.
Recently been gigging, for pay, with a new group where playing tenor from a C fake book
really keeps the reading sharp.

While reading and writing on this topic, I was reminded of the post "are singers musicians?"
In my opinion being able to read is one of the factors in determining my evaluation of a singer as a musician.