Another point I thought of later, while I like the islander for its looks etc, not sure of the cal's looks off the top of my head, the islander anyway, was designed at the height of the IOR rule with the pinched stern etc, and will roll going down wind a bit if you're not carefull. Where as the C310 I believe may have a better sailing form hull. So a little more for a newer boat with a more seakindly hull may be the better option here.
She drives me boat,
I drives me dinghy!