Don, I am the proud owner of two 100LG (Medium & Fine), one 150 & one 200-20 "detail". All sharing the "old style" head. Everything in front of the body is interchangeable. Of course the needle length required for the 200 stops me from using spare needles from the 100/150 series. I have a Large head and needle for the 100/150, but have never bothered to use it. I also have a cheap Badger 350 clone that I bought for less than $10. It fills out a space in my tool box, and serves no real purpose, though my wife used it last year for painting some stepping stones for our garden.
Badger 200-20 Detail Air Brush:
What sets this air brush apart from the other 200's is the 'guardless' spray regulator, the handle and the needle adjustment control. It comes with the medium head and needle.
The spray regulator lacks the "crown" that comes with most airbrushes. This leaves the tip of the needle exposed, so you can get incredibly close to the surface with the tip. This allows for very thin lines. It also exposes the tip to damage, and one must be very cautious to retract the needle during storage, and to replace the tip protector before putting it down, even for a second.
The handle has three O-rings held in place by engraved grooves, and allow your thumb to grip the handle firmly. Important when your needle is exposed and is a hairs breadth from the surface! The handle color departs from Badger's blue or chrome finishes, and I'm not really a fan of the shade. But, c'est la vie! I would hope handle color is not the deciding factor in a person's decision making when it comes to an air brush!
The needle adjuster is graduated and registers with a mark engraved on the handle. This allows you finer control and repeatable settings.
Your review is spot on with the 200 series ability to spray fine lines and is very easy to use and operate. I would put my 200 with it's medium needle up against my 100LG with the fine needle, though that may be more a lack of talent on my part. It certainly requires a deft hand to keep lines consistent with a dual action AB!
My 100LG M is the air brush that is used most often as I find gravity fed airbrushes a bit easier to clean, but the 200 comes out when I need to spray very fine detail. My trusty old 150 sits in its case most of the time, but I do bring it out on occasion, mostly when I'm spraying a large area.
You are correct that a 200 is all most modelers really need, however I still feel that if a person is limited by budget to buy only one air brush, a dual action is the preferable choice. They have a slightly wider range of capabilities. Now if Badger was to offer the 200G on their garage sale website...
Speaking of which, they are offering a 200-19 detail set for $44 complete with braided hose. I'm not sure what the difference between that and the -20, but mine came with the color cup, and the -19 only comes with a bottle. Heck of a deal! Other deals in stock is a 150 (air brush only, no cups, bottles or hose) for $35.20 and the 100SF in both LH & RH for $30.80.