I just caught back up with this thread, and didn't really want to argue the fine points of 0.2mm pen tip (which is 1/5 of a millimeter, and not that thin!) versus a brush tip. So, a photo is worth a thousand words. Left: 6/0 Raphael 8404. Right: Sakura Micron 005. Photo taken side-by-side; the Raphael is about 3 months old, the Sakura practically unused.
There is no way anyone can look at those two and say that the Sakura is even remotely close to the 6/0 brush. Forget about the detail you can achieve by just lightly painting with the tip of the brush; even if you press down, or use the top 10% of the brush tip (to draw a line, say), you STILL have a line that's 1/2 the size of the pen. Remember, there are script liner brushes too (the ones with long bristles).
I am not saying the Sakura isn't easier to use. But the skills you need to draw a fine line with a 6/0 are the same skills you use to do lines with all sorts of different paints for your edge highlights, detailing, and everything else, no? Plus, controlling a pen so that the start, middle, and end are consistent and also just the line (no fat dot anywhere) is also a skill requiring practice, much as it is to draw a line with an airbrush.
Also, one could say, since pens are easy to use (if only because we've written with them our whole lives) why not just paint the whole miniature with liquitex acrylic paint pens?