This appears to be a subject that comes up pretty often. As far as gearing goes, I'm in Martins camp. When I first put "Bluebird of Chelsea" on the water it had 2 geared motors.....and you could hear the whine of the gears across the width of our quite large lake. I also found that I hade no reserves of speed to escape the "keep death off the water" brigade. My models range in weight from 20lb (Bluebird) to 120lb (Gold Ranger). All are direct drive but using the ESC to keep the potential speed down to a near scale speed with plenty in reserve....especially when stopping a heavy one. I've generally used Smiths heater motors, but also car seat motors which I find are better for my bigger models. "Chipchase" also warned about some heater motors being of "low torque", mainly motors from vans, trucks etc. So be careful. Until someone disabuses me, I still think that the better Smiths motors are the same as Barracudas. All are low drain, oodles of power even with a 4" prop attached. But, as I said, moving a heavy model is easy, stopping it takes the power.
BY.