Well to me the first thing I noticed was that it seemed to break up the clear much better, and had a better/more even pattern, and it seemed that when i used the Iwata I could get away with using less air pressure, and still ended up with a smoother finish,, and by using less air pressure, you should have less dirt "in theory".. I also liked the the way it felt as compared to the sata. You might be able to call it dumb luck but my paint jobs have been looking much better since the switch, better layout and less dirt.. but I have recently switched to SPI, so maybe it's just a good combo,, but I have tried the Iwata with the global clear and still prefered the Iwata.
Another thing that really appealed to me is that if i needed to buy parts for the Iwata, I don't have to purchase a whole tip set like I do with the sata.. the last sata tip set i bought was almost $150.00 and if I want to change my 1.4 to a 1.3 it doesn't cost nearly as much because you don't have to buy everything to switch...
and another thing was the grade stainless they use on the needle is a higher grade stainless steel.. although I never wore a tip out on my sata so not sure if that really matters.. My digital guage on my sata just went also,, never looked at it anyways.
I'm not trying to say I don't like Sata, just saying what I like about the Iwata that made me change.. I actually have 4 sata's now, and use them for different things, and always said I would never use anything else,, untill I demo'd the Iwata.. now i use my Nr 95 for single stage, my NR2000 for base, a jet 90 that I dont' touch any more,, and my Rp that I use to use for clear, but havn't used it since the iwata,, not sure what i'm going to use it for yet..
hope i didn't confuse you with my nonsense..lol...