Gary, I don't believe that one instrument is easier than another. While the guitar may look as the easier instrument, looks are deceptive. An instrument is as complex as the one playing it. That's why we have mediocre players, great players, fantastic players and virtuosi.
A fantastic arranger player will most likely be as adept at playing the organ or piano. What do you think would be his first choice? Either the piano or the organ.
Bo pen nyang.