My choice is to use a sail arm rather than a drum, and I use the Hitec 805BB ($39.99) modified for 180 degrees. Couple this with a Spektrum DX6i, and you have a fully programmable system that rivals the flexibility of the Smartwinch. The Spektrum allows exponential control for fine tuning with very high accuracy. Also, since all of the intelligence is built into the radio, not the servo, you can keep a spare in your kit and swap it out pondside in a few minutes. I don't think you would be able to quickly change out a Smartwinch between heats at a regatta, your day would probably be over even if you could afford to keep a spare on hand. For $39.99 each, if you do happen to burn one up on a high wind day (never seen this happen yet) you can always keep spares handy. I use five cells and get 343 oz/in of torque, which is plenty.
Dan