I only have the one set (.18) on my Micron, but I have multiple size sets for both my Eclipse and VL.
My experience with those is that the size doesn't pertain to any relative "ceiling" in terms of line width or quality. You can ultimately pull the same thinness and quality lines with the larger size as with the smaller.
The difference is a trade off between trigger handling and paint reduction/pigment size. A smaller nozzle/needle gives you a broader response curve in terms of paint volume-to-trigger travel, making it much easier to find and hold the "sweet spot" for fine lines, as well as giving you better general control over line width at the "fine" end. It's easier to do a tiny dagger stroke with a smaller nozzle/needle, as trigger travel between the beginning and ending widths of the stroke will be larger.
I can do Micron-thin lines using my Eclipse with the .5 nozzle/needle installed, BUT the trigger sweet spot is so tiny it's basically an on/off switch that takes very careful finger control to hit. I can do the micro lines, but forget micro dagger strokes, and a needle stop would become desirable for repeating lines, whereas I never really use the stop at all on either my Micron or the .3 set on my Eclipse.
The cost of that is the brush will have less tolerance for paint viscosity or larger/irregular pigment sizes as you go down in needle/nozzle size, as the passage the paint has to flow through at the tip becomes both narrower in an absolute sense, and narrower relative to its length. The venturi effect has to work harder to pull more viscous paint through a narrower passage, and large or irregular pigment particles have more opportunity to bind and clog in a narrow passage.
This means you can sort of get the benefits of a smaller nozzle/needle without the viscosity/particle size drawbacks by switching to a taller trigger. Though that of course has it's own ergonomic tradeoffs.
If you were to ask me what the difference is between a stock Micron and an Eclipse with an extra tall trigger pad mod, I'd say better atomization and ergonomics on the Micron, more forgiving paint tolerance on the Eclipse, but not line width or control.