I too, am considering a power windlass and have done some research into this subject. Generally, the primary reason for a vertical windlass is the minimal clutter/machinery on deck. This is not the windlass of choice if your below deck area is inaccessable or in the middle of your v-berth. The horizontal windlass however bolts on fairly simply and has no below decks intrusions. The added advantage of the horizontal windlass is that you can use it for other purposes such as hauling an individual up the mast via a halyard. If your anchor roller is above the deck (ie with high bulwarks) you need to use a horizontal windlass as the vertical windlass requires a level approach of the rode from the roller to the capstan/gypsy.
I have questions on the manufacturers of windlasses and their products. Ideal, Muir, Simpson Lawrence, Lofrans, Lighthouse, Maxwell all produce a horizontal windlass in the 1000 to 1200 pound load category. Are they all created equal? Are they all supportive of their products? Is reliability a strong factor for each? I would appreciate any personal information that anyone can provide either here or via email direct. Thanks, -Jeff Hubbell