Like a lot who have written here, I do some of both. I learned to read "reasonably well" as a kid, and use that to help learn new songs. I also had a habit, for many years as a kid (even into college age) of "playing along with the radio", that is, listening to various stations and trying to play along "by ear" - I did a LOT of this years ago, and I think it helped my 'ear' quite a bit.

These days, I tend to learn new songs best by hearing them (esp. good is hearing various renditions and not just one), and if I have a "fake sheet" (or full score), the listening plus having chords/melody, makes learning that much faster.

I find that I may have a chart up (on my iPad) but for many songs I'm playing say ~90% by ear/memory; the chart is just there as a guide to the overall arrangement and I look at it now and then but not constantly.

I do find that I've become, as some people say, "lazier" in that I rely on charts more now (at 55 years old) than I did a decade or two ago. One reason is that I have ~1,200 songs in my repertoire, and I just can't remember the overall arrangement and some details, for all of them. So these days, there are maybe ~200 songs that I can play from memory, but for the rest I need the chart just to get me started, or to help with some chords I might forget.

I've also noticed that my (5pc) band likes having charts available for more tunes, whereas years ago we had no charts on stage. Just our aging brains, I guess! :-)

=Jim=