I started with these three and two others in my evaluation.
After seeing the Shaver I decided to spend a few $ more. It really is hard to believe in this day an age that anyone thinks that is acceptable build quality but they sell a lot and many people make them work. Some people build ther own and with two days of welding training and the plans I could build a Shaver.
The Legend has a big door and firebox and holds lots of water which acts as a buffer. The double pass flueis easy to clean, I don't think it smokes that much and the large water reservoir reduces the starts and stops which is when it puffs out th emost smoke. I bought the bigger one because of the bigger firebox and water because it reduces my woodcutting (longer peices) and loading. The legend has a bit thinner box than some, I think it helps with efficiency (heat transfer to water) but some will tell you you should ave 5/8" steel (Shaver), in which case more heat goes up stack. The other think I liked about the Legend is that very little empers come out the stack (safer), If I burn paper in it with the blower going I might see slight embers in the dark. The double pass reduces the hot ember issue. The Shaver is direct stack and made me nervous. I forget what NC does with the exhaust. I didn't know what to think about the 'anti stainless steel' rhetoric. I suspect the good stainless steel models are proven but there must be some issue with some stainless and stress corrosion cracking. I could find no complaints about the Legend or the NC.
The Natures Comfort would have cost me more both in price and shipping, had I been closer to where the NC is made the decision might have been different. These OWB's tend to be regional due to shipping costs so what is preferred in Vt is different than NorthCarolina. The NC has a smaller firebox both in height and depth as well as a smaller reservoir but it does look like a nice unit. If I had a smaller house it would have been more interesting.
You start with a Shaver Budget and then end up having to limit yourself at some point. One thing I saw was that the piping, pumps, etc on my project practically doubled the cost of the Shaver. See a couple burn, look at the brand Yoder sells also. I always have 'buyers remorse' but so far I am happy with my Legend 6180. I'd consider a gassifier if I lived closer to neighbors but I doubt they really smoke much less at startup and idle. Also they are relatively new and I like simple/proven. If you buy wood I'd suspect a gassifier has a 'payback'. I figure a payback inside 5 years with a happier wife and at least a ten year life. And some better health from doing some 'real mans' work.