U13 is on the right track when he talks about playing with feeling. Another thing is a lot of people who read sheet music don't really understand the music in front of them. They don't see the "theory" in the music, they just reading notes (and other symbols). Once the notes run out, they have nothing else because their mind didn't kick in to understand what was going on.
In order to play by feel, you need to know what you feel. You need to know that certain chords played in the right order will give you a certain feel in the end. This is what gives ear players a slight advantage in improvisation, even if they don't know theory. They know that playing a certain sequence of chords, a certain run, etc. will bring about the feel they want to convey to the listener or even themselves.
So, it's better to have a balance of both skills. Being able to read music is great. But couple that with being able to improvise after the music runs out and you will be a great musician.
I'm currently majoring in Music Edcation in college and they have me playing a lot of classical stuff. Before I play a piece, I take it apart using theory to understand it. Because of that, I can learn the piece how it's written, then if I want to improvise or play it in another key, I can do that cuz I understand the music.
In gospel, I have no sheet music in front of me. So, I rely on my theory and stuff that I've practiced to help me learn gospel. There are patterns to the "Pentacostal/C.O.G.I.C." style of music, but many that play it don't know the theory to be able to communicate those ideas to others. I'm trying hard to change that on this site.
Believe it or not, the patterns in music are the same for every genre. Every genre uses 1-5, 1-4, 2-5-1, 7-3-6, 5-1-4, etc. progressions. The distinction comes in with the types of chords being used, the musical instruments, the runs, etc.
