I have presented this question to several trainers but have never received a definite answer. I am right handed and right everything else but for some reason my curl strength is less in my right arm than my left. There is a small but noticeable difference in bicep size, the left being larger.
I work both arms individually and equally but the left can always do more repetitions at a lower weight or more weight at one repetition. Only possible issue is I had the right shoulder scoped 20 years go for spurs and impingement. I have no pain in the shoulder when lifting.