Go with the Raritan SeaEra...it's the most durable reliable electric toilet in its class...the only one I've never been asked to trouble shoot since the day it came on the market. And it's available as a complete toilet OR a "conversion" (everything but the bowl, seat and lid) in both sea water and pressurized flush versions.
Sailingdog, there's really no reason to avoid an electric toilet on a boat with only one head...it'll chew up most things that would clog a manual toilet...easier to unclog if it doesnt'..most only draw 10-16 amps (except for the Jabsco "conversion" that draws 24, makes enough noise to wake the dead and has the shortest trouble free lifespan of any toilet except other Jabsco toilets)...and in the event of a power failure that leaves you unable to flush it, you'd have other problems that would make that the least of your worries--no nav lights, nav equipment, communications equipment...but you WOULD still have a bucket!