I have played diatonic harmonica since high school, beginning after hearing a Charlie McCoy recording of Shenandoah. I purchased my first 10 hole harmonica and messed up by not tracking down some advice and instruction from an experienced player. It was 35 years later before I took a beginning course with JP Allen and then Michael Rubin. I also made great progress from what I l learned from David Barrett at BluesHarmonica.com.
I love the country style licks made popular by Charlie McCoy, Buddy Greene, and Todd Parrott. That style is what most people associate with popular harmonica playing. So my plan is certainly not to abandon my development with diatonic but add Chromatic playing for the unique sound it offers. While you can play the Chromatic by ear, a lot of people learn to play the instrument from sheet music which opens up a world of popular music. I hope to be able to play both by ear as improv and play from sheet music.
The chromatic "sound" is more orchestral or Jazz in the way that a Sax or clarinet might be. Lets face it, country style licks and note bending are always the best fit for playing with many type of music and bands. Since my interest is playing Gospel in church venues, the chromatic would actually be a better fit for many traditional hymns. Here is Chris Bauer playing "Turn Your Eyes Upon Jesus."
My decision to master the chromatic is then my effort at advancing my knowledge base as a musician. I can only imagine some day that if I am playing any tune I want from sheet music, that it will also make me a better more knowledgeable diatonic player.