Gunner, both units can be 'electrically' disabled - e.g. with the Air-X, a switch can be put in-line that will backfeed into the stator, thereby suspressing rotation and 'braking' the blades (which will just slowly turn). As Jon says, the units are very different and a thorough reading of the specs for both would be a good idea. E.g. I believe the Air-X has the ability to manage a 3-stage charge; I don't know if that's true of the KISS.
Any wind gen you mount on your boat is going to produce two kinds of 'noise' - blade noise
and vibration, the latter being transmitted via the mounting pole, rubber isolators, etc. Particuarly where wind gens are mounted above aft cabins or adjacent to the cockpit
(the "crew rest area" <g>), you may have some issues with a wind gen. Your best bet is to find a sample of each aboard boats on a windy day and form your own conclusions.
Finally, these devices have a finite lifespan afterwhich some service
or replacement is needed. Depending on how long you plan to use your new unit, you might want to consider who will service
the unit at what cost. AirMarine has an upgrade path for their 3 generations of models, which over time might come in handy.