The amount of 'pull' (torque) applied by a servo is determined by the strength of the motor in the servo and the length of the 'arm' or radius of the drum for the winch. The smaller radius of the drum is just like having a shorter servo arm. Shorten the arm by half and you double the amount of 'pull'. 'Course, you can't pull quite as far since the end of the arm travels a shorter distance. A sail winch isn't limited in the number of turns it can make like the typical servo (only part of a complete circle). A typical servo can be made into a 'winch' by removing the internal control that limits the motor's travel. The 'catch' to that is that first you gotta remove it from the boat, disassemble it, remove the correct component, re-assemble it, make the @#$ drum, and fit the whole mess back into the boat. (Just buy the silly thing, much easier/faster.)
Servo and arm or a winch, both have their 'pluses' and 'minuses'. The two biggies are cost and amount of travel allowed. You pays your money and takes your pick, as I'm told they used to say about something else that sounds like wench/winch.
Pulleys. Or maybe 'block-n-tackle'? It/they can and will multiply the amount of force exerted in pulling on the rope. The draw back is that they will require a longer rope, or only pull for a shorter distance with the same length rope that you started with.
What's your -best- choice? Beats me. You decide...
- 'Doc