For the past 14 years we have had Sealand china toilets and were quite happy with them. For the past 9 year we also had the Techma toilet. This too performed very reliably. My only problem with the Techma is that when we are dry camped for an extended time period, the Techma uses more water than our manual flush toilet used.
Several months ago we purchased a new motorhome. It came with a Thetford china toilet. We have both been amazed at how much better it flushes with less water than our Sealands did. With the Sealand we almost always used the hand sprayer. With the new Thetford we hardly ever have to use the sprayer. This may be because the Thetford is 9 years newer than our Sealand was, but it's just our observation.
Ed Headington