Well, I personally have seen that there is a price difference - but it is not massive unless comparing against a Spectra or other 12v, high end model. I have always felt the big positives are that you can make a LOT of water quickly, and if it breaks, YOU know how to fix it. Go look at a Spectra to get a feel for what I am saying.
The negatives are that it is labor intensive, it is much larger than the typical commercially available units, and it may make too much water for you. The rule of thumb I have always considered is that you want to run your watermaker everyday or every other day to keep them membrand nice. WHen you start pushing off to a week+ between runs, you may have a problem with junk building up on the membrane and a premature death.
Note: Dad has a watermaker, not me. His is the SPectra. Nice unit, totally automated, and if that appeals to you and money is not an object, it is a good choice and good product. It is also the most efficient. I am either going to purchase a unit that is of the homemade variety (go here: Aquamarine, Inc - Home
as I have seen on eof their products and that is all they have done) or I am going to make my own. I can use the large water cap and I personally want something I can repair and diagnose on my own. This does not appeal to everyone though.
PS You need a generator (unless you are really creative and can run it off your main and have the power to do so). I am not sure a 'Honda' would push it. If you do not have one, take it off your list.