I suppose it depends on what your using it for and how “flexible” it needs to be. I used candidate #2 when I made my laser engraver from scratch.
Candidate #1 appears to be identical to #2. They both employ a spiral cut that essentially turns them into thick springs that allow flexing movements perpendicular to the shaft, but relatively little compression/expansion and no noticeable relative rotation.
Candidate #3 appears to allow more flexibility?? Maybe it transmits less sound?? I have no experience with them.
As is all too common, 3DPCs descriptions run the gamut from basically useless to non-existent.
It’s pathetic when you have to search other company’s web sites to get more info on 3DPCs product selections. Looking on Amazon, some of these models are described as having electrical insulation properties (ie. the nylon completely separates the two halves) but other than providing isolation from static electricity, I’m hard pressed to think of where this would be useful. It’s also described on Amazon as providing some vibration damping. There are stepper motor mounts that do something similar: separate the stepper from the frame with a nylon cushion, but really, it’s not the steppers that are causing the noise, it’s the timing of the signals that drive it, so if noise is what you want to get rid of, you’d be better off killing it at the source by using silent stepper motor drivers.
So, in the end, I can, and did, and would again, go with candidate #2 but I can’t give you a really good reason why in relation to the others.