whichever one feels the best...actually i take turns so they don't get jealous...the last thing you want is a hand fight while trying to get off...if my feet could reach my cock i would use them too...oh well...
I'm right handed by I jerk off with my left. I dunno why, I just tried it that way when I was younger and it was better. Plus I can still work the mouse with my right hand
I use to only masturbate with my right hand. Then I broke my arm and could no longer use my right hand to masturbate so I learned to use my left. Now I start with my right and when it gets tired I switch to my left.