I don't know what the best brand is, but we're very happy w/our ShurCo (ShurLok) elec tarps.

http://www.shurco.com/ag/3500series.html

We've had 2 of them for a year and a half now. They work fine in wind conditions we have here. They'll certainly roll in wind that we could never have handled a crank-tarp.

We did have a motor burn out in one unit, but it was replaced free. Not sure why it failed. The motors are protected by a circuit breaker @ the battery connection. It had never tripped. It just slowed & stalled one day.

If we bought another trailer, we'd put on the same electric tarps.

Here's a YouTube movie of our installation.

http://www.youtube.com/watch?v=6pnuEhuPSQI