I was thinking some of what you've said - but without experience to back it up. Winches might be more prone to failure, but I'm also concerned that an actuator that can fit in the box when it's retracted won't have the stroke length I need to lower it all the way. The box is about 6" deep, on the outside, so I'd need an actuator that can fit in about 5 1/2" but still have over a 10" stroke.
I've been thinking more of winches or a single winch that would play out a line on each side, like what you were talking about with 2 actuators. The last time I could look into any hardware at all was in the '80s, and at that time, finding two motors (other than stepper motors) that could be counted on to wind up (or down) at the same rate wasn't always easy.
Do you have suggestions on sites to go to for buying actuators or winches? Most of the ones I'm finding seem more for industrial or heavy duty use.