I' ve always shot split on my sticks and compounds with sights and 3-under when I shoot my compound barebow. I' ve been experimenting with shooting 3-under with my longbow and it feels better on my arthritic ol' piddies but, after so many years of shooting split finger, it does seem wierd. Maybe I' ll get used to it.
Like Chad said, 3-under is against the rules at some tournaments, but I' ve got more than enough tournament trophies already.