I prefer the badger design but again just a preference, not better or worse.
I's a matter of giving/allowing the user more options.
Like many others, I remove the air cap on my Iwata Eclipse when in use, and basically only use it to protect the needle when I'm not using the brush. Badger brushes come with a protective end cap (not air cap) for this purpose, so I don't really miss anything there. My SOTAR came with a pronged hold down ring, and I made a prong air cap for my Eclipse back when I first got it, but I don't use either anymore, as they do actually get in the way with ultra-close stuff (the prongs are only barely longer than the needle, but that's the needle at rest: when the needle is pulled back for spraying, it's easy to end up closer to the surface, so prongs can still get in the way)
So the the Badger way of doing this wouldn't bother me personally either...
...However, in the bigger picture I think a design that can allow more users can do as they wish with it, without generating any downsides in the process, is an objectively better design. The Iwata/H&S/Grex/etc. type nozzle cap does this. The Badger one does not, and offers no benefit in trade to justify the lack. There's nothing to actually
prefer with the Badger design, because there's no advantage (it doesn't even make it lighter or simpler or more streamlined), only something not to miss if you, personally, don't use it.
The only advantage the Badger nozzle cap design confers is to make manufacturing slightly simpler for Badger. Though not likely by enough to make a cost difference to the buyer, given how the alternative is pretty standard on other brands regardless of price point.
If I were them I would just spend some research on a decent quick coupling with build in MAC valve. Or even make a replacement for the stupid proprietary connection. They don't us it on the SATAgraph 4 so why still use it.
As a SOTAR user who likes to keep the stem as short and light as possible, I'm actually quite glad for Badger's fitting, because it's significantly more space-efficient than the more standard 1/8 BSP fitting. What I like about the SOTAR (particularly the side feed) is it's pen-like handling, and a light Badger hose connected directly to the brush is very nearly like holding the brush without any hose or other fittings attached at all. Unlike the nozzle cap design, the proprietary air fitting does have an advantage. An advantage which, like with the Iwata/H&S/etc nozzle cap, is subject to preference, but an advantage that actually exists to prefer, unlike the Badger nozzle cap.
Badger already does have a both a male quick connector connector that fits other brands' female connectors (the male/female bits are standardized, so this is true of all brands), as well as a MAC valve quick connector of their own.
Is the SATGraph made by Badger, or by SATA themselves?