The nozzle head is part 5. On Iwatas and other designs this isn't a separate part from the body. I think Badger made it a separate part so they could use the same bodies for multiple models with different head assembly designs (or vice versa)... maybe? Not sure why. Anyway, this SOTAR version is like Iwatas and Paashes and such in that this isn't a separate part, although it still appears to have been machined separately then soldered on, as opposed to machined into the body itself.
Paint wise it's pretty similar. Spray is a little fussier with the trigger at a low paint volume position, harder to to get lines as fine without the spray stopping, but I don't know if that's the needle and/or nozzle's fault. I had polished the needle and lapped it to the nozzle on my regular SOTAR, so the next test will be to swap those parts and see if there's a difference.
The needle itself looks different. The metal looks like it has a lighter tone, and the shaft is not as smooth, with a diagonally lined diffraction pattern from lathing tool marks (said diffraction may account for the lighter tone, not sure).
The air valve spring is much lighter than on my regular SOTAR. My regular SOTAR has an extremely stiff air spring. By far the stiffest of all my brushes. Enough so to make controlling the needle a little difficult, as I have to press and hold down hard while trying to move the trigger back and forth precisely. I'd been wondering if Badger air springs were moddable because of this. However the trigger on my side-feed SOTAR is quite comfy.
The gritty/scrapey trigger feel I noted in my review of my regular SOTAR is present in this model as well, but its slightly different. I've actually figured out what the main culprit is. The sides of the trigger cutout in the body are slightly rough edged, and the way the trigger sits on the valve allows it to swivel within the cutout. As a result, when I pull back on the trigger, the trigger will sometimes twist slightly in one direction or the other, causing the edge of the flats on the sides of the trigger stem to rub along the striations on the cutout edge. This is not the only culprit, but it is the largest.
The side feed model is slightly better in this regard, as the cutout is slightly narrower, and the edges are in the vertical axis cut/ground straight (parallel with the trigger stem) rather than at an angle radial relative to the body's axis (which is the case with the regular SOTAR). This constrains the trigger stem so it can't swivel as far, and thus can't present the edges of the stem flats to the striations in the cutout as sharply. The striations in the cutout edges on both brushes also run diagonally across the faces of those edges, so having those edges parallel to the trigger stem means the striations overlap and act partly like rails, reducing the vibration from the stem edge rubbing along them.
I feel like maybe I need pics/diagrams to make that stuff properly clear, sorry.
The scrapeyness is smoother on the side feed, more like sandpaper than the more grindy sensation I get with the regular SOTAR. I can smooth it out further by putting some K33 there, but there's still abrasion going on. In fact, the brush arrived with scrape marks on the trigger stem from this already (presumably incurred during factory testing). TBH, after two brushes with this, I'm starting to be surprised that no-one else has claimed to notice or experience this with their Badgers or SOTARS. One brush might be an anomaly. Two starts to feel like it's maybe a problem with Badger's manufacturing. Not gonna lie: as long as their machining is rough in these places, they are wasting both their and their customers' money with alleged special coatings. The lack of finishing in these areas completely invalidates the whole "glydercoat" thing Badger likes to tout. Fancy coatings won't matter if the contact surfaces are not smooth enough to begin with.
My HP-CS does not have anything like this sensation. Between the heavy chrome plating, the trigger stem being thicker (i.e. the flats are wider) so it can't swivel in the cutout nearly as much, and the machining just being smoother to begin with, the trigger moves perfectly smoothly.