I emailed the head airhead at AirHead (sorry couldn't resist!)
about the recent changes to the product, and Geoff replied thusly:
Geoff also included a copy of his take on the differences between the AirHead and the Nature's Head:
Warren

The improvements I have made over the past year are subtle and are not evident on the website they include:
1. Improved liquid separation.
2. Stainless bowl ring (was anodized aluminum).
3. Improved bowl to base seal (twist to lock) means the screws are now captive so you no longer need to remove them (and possibly lose them).
4. Improved manufacturing (we can ship in two weeks).
These improvements come from years of talking to customers and endless thought on how to make things better. I haven't really made a big deal out of my improvements so I have to wonder if people are talking about my product or confusing it with "Nature Head". Those who sell it haven't been real quick to correct people who think I designed it....I didn't. (I've got my comments below), However the design is frankly is a direct knock off that has only one benefit as far as I can see which is the seat size.....but then again it doesn't really have a seat does it?.
Oh, Air Head will have a larger seat soon.
Geoff also included a copy of his take on the differences between the AirHead and the Nature's Head:
In regard to your email request regarding comparison of the Air Head Vs. NH....
In my slightly biased opinion you are buying a more thoroughly thought out product when purchasing the Air Head. I've been at this since the late 90's and have sold 100's, and I have spoken to 100's of customers and when there is an issue with the product I make design changes. If there is something that I think can be improved I improve it. So over the years I believe I have created something that is solid and dependable and I have made countless changes that really aren't noticeable to people. Air Head is designed to last into the foreseeable future. So the chances of someone fresh copying Air Head quality and dependability is remote right off the bat. They just can't have the breadth of understanding that I have. During FMC's tenure as an Air Head dealer he sold about 10 units....
NH is designed to be manufactured more cheaply probably because they figured they needed some advantages over Air Head since its reputation is so good. However, in the cost cutting they have taken some shortcuts:
* NH translucent bottle will get pretty ugly pretty quick due to build up of residue from urine. Air Head has a view strip with a replaceable PVC tube. If the tube gets dirty replace it at any hardware store.
* To remove the bottle of NH you need to lift the bowl exposing the solid "goods" for a few seconds. Air Head liquid tank is pulled out using a pull at the bottom the bottle tilts under the spout. The Air Head bottle has 1 3/4 gallon capacity when used as designed. However, it really has two gallons if you lifted the bowl as you do the NH. In fact I"ve seen them demonstrate my product that way. It used to annoy me.
* There appear to be no carrying handles on the NH solid tank!
* Air Head comes complete with a solid tank transport lid when you carry the tank off of the boat. You might check to see if NH comes with a lid for use when you empty the solid tank, I haven't seen one.
* Air Head comes with starter peat moss, liners, enzyme, mounting screws, hose, fan, four pages of illustrated instructions edited over the course of six years. I'm not sure what NH comes with and the instructions are brief.
* the lid of the Air Head has seals. NH has none.
* My favorite: You can lift the seat and urinate into the Air Head like a real man! NH requires you to run a stream over the seat that does not lift. I understand that we mariners will in rough weather sit, but isn't it nice to stand when things calm down?
Size:
Air Head measures 17.5" front to back see, attachment. NH seems to be deeper:
FIrstmatescabin.com says:
17 ¾ inches front to rear, and is just under 20 inches tall. It also features a full size molded-in seat for safety and comfort.
A dealer, "ecovita.net" says:
Measuring from top: 18.75" deep (+ about .25 for rear hinge); another inch is necessary when the lid is up, so factor 20" depth.
Hmmm FMC seems to have left out some pertinent information.
Warren