Both the ability to 'play by ear' & music sight reading (from sheet music) are equally important skills for becoming a better musician. If you can only play by ear I encourage you to start learning to read music (at least a lead sheet/chord chart). This is essential, especially if you desire to play good musicians, and it helps insure everyone is on the same page, In addition, the ability to sight read music INCREASES your ability to pick up & learn a LOT more songs & expand your repetoire musch faster than playing by ear alone offers.

On the other hand, if you're only able to play with written out music in front of you, this too has serious drawbacks. I've found that some keyboard players who can 'only play' this way tend to sound stiff, because instead of LISTENING to what they're playing, they rely on the playing the dots on the paper, like a word processing typist does, and lack musical 'expression'. Dots (notes) on the printed page are only a written out approximation of what the song really sounds like because artistic phrasing & nuances of a melody (expression) cannot be captured from dots & music notation alone.

In conclusion, I feel that being able to play BOTH by ear & from written out notation essential skills. For my playing, I utilize BOTH skills together when playing. If you're weaker in one skill than another, spend the extra time to improve the weaker of the two.

Scott