I've been working at a high surface area and normal to slightly above normal volume boards with flatter rockers. I've shaped two, and I surf east coast of the US. I've been liking very short boards, I just finished a 5'4"x20.75x2.3" which I've yet to test ride. But it has the ingredients to go well in smaller surf. If you want a small board, look for surface area, a bit of extra volume and flatter rockers. Longboards don't have that issue obviously. I used to ride a 5'7"x18.5x2.75 twin fin with really flat tail rocker. That worked too, but I knew how to surf when I started riding that.
Go into your local shop, see if they can tell you what works well in your waves. Or if a local shaper makes something cool. Also I've never been anywhere near 6'1", so a little board might be strange for you. I don't know, I'm 5'5". Chances are you could get a full custom board by your local shaper and pay the same or less than a new rusty or something.
And for learning, of course picking a 5'7"x18.5"x2.25" performance shortboard with crazy rocker will get you nowhere. But good positioning and wave choice will go very far, so learn where to sit. A huge board will help, but there's no reason to paddle like a mad man to get into a wave when you could sit further in, take a few strokes and be in the wave.
