This is one of those little things where most people probably wouldn't notice it and it does not directly affect playing.  But I really didn't like the volume, tone and power knobs that my electric violin came with.

Maybe it is just an electric player sort of thing or maybe it is kind of like how some people with acoustic violins like tuning peg that are carved to be a bit fancier than the plain ones.  But it does affect the look of the instrument a little, and the feel of the control when you adjust it.  It is also one of those things that can individualize an instrument just a little.

What I didn't like about the factory knobs is that they looked and felt cheap.  Tall, sharp edges, all plastic, and they were small in diameter which made them feel too "twiddly".  Google had their little thing up for Bob Moog's birthday the other day, and it reminded me that I had an old set of "communication style" knobs somewhere in my parts bins that are a bit more like what he used on some gear.  I've had them for some years, but I'm pretty sure they aren't old enough to be anything I bought off him when he had a little place here in town.  I think they probably came off an older BOSS guitar FX pedal by the look of them.

Anyway, the main difference in actual quality is they have a brass sleeve inside that is tightened onto the shaft for the control with a little brass set-screw instead of just being a bit of plastic held on by friction.  The base of them also is up off the surface of the instrument by a millimeter or so, so they do actually turn smoother.  Mostly they just look a bit nicer and I like the feel of them better.  Smoother on the top so they are less likely to catch on clothing or whatever.

A very minor sort of upgrade, but Google reminded me of Bob Moog and this set of knobs has a bit of "old synth" as opposed to "real cheap guitar stomp box" look going for it.  The bottom pic is the "upgrade" ones.