A few years back I did some recordings with my Zoom H4, same room, same stick, same cymbal, same felt, not top felt or wing nut, same recording position, same playing pattern at the same force (as much as I could) and trying to document a difference between having a boom stand extended and a straight stand (the stand is one of those designs where you can hide the boom down inside the top tube and turn it into a straight stand). Using my ears it seemed like having a boom stand with a long extension was resonating with the cymbal making for a change in the sound. I couldn't pick anything in the recordings.
In a similar controlled fashion (at least the best I can manage -- I'm a scientist by day) I've found that felt size does make a small difference going from one which is quite a small diameter one to a great big one. Smaller felt = more bell = more high frequencies in the mix. Similarly putting a large top felt on reduces the bell. But these are teeny tiny changes and would be lost in the music.
The reason I was doing these things is I have a "problem" cymbal which has some high frequency build up which I was starting to find displeasing. You can hear it by clicking on the sound file at http://black.net.nz/drums/
When a few others listened to this recording they decided that I have the "problem" not the cymbal. I'm being overly sensitive.
What I have discovered is that whether or not the cymbal sound changes seems to depend on the individual cymbal. I've got some which seem to be slightly (these are all slight effects again, lost in the music or from the audience listening distance) affected by changing
slope from closer to horizontal to closer to vertical
felts
tape
stick tip (and general diameter)
Given what I've found so far I'd say it is possible that those who say certain stand attributes change cymbal sound may be right. And those who say certain stand attributes don't change the cymbal sound are also right. And the difference between these situations? Different cymbals, as well as different everything else. But from my experiments different cymbals is enough (all on its own) to account for almost all these different experiences.
Individual cymbal variation certainly doesn't rule out the effect of different stands in certain situations either. I had quite obvious sonic effects from clamping a 12" boom to the tom holder on a 10/13FT/15 microkit. I was trying to save carrying a cymbal stand (as one does) but the results were not pleasing to my ear. Too much resonance between the 10" tom and the cymbal.