I've considered there are too many choices and our perceptions of those choices can affect our decisions to move forward.
If you didn't know there were three Feather holders or more than one or two Feather blades, if you wanted to learn to use a RBSR, you would adapt to whatever was available. You wouldn't think the SS is mild and the DX is less mild.
I had no idea there was but one holder, the SS in 2018. I used the Pro Guard and moved to the Pro Super not knowing it was wider.
Good point, but more to do with choice and availability.
I’m suggesting that the slightly different design these RBSRs causes them to react and respond differently when you change the blade to another variety.
Based on my years of playing guitar, the phenomenon is a repeatably observable result when changing string alloys and or gauges on an acoustic guitar. They sound and play a little (sometimes more than a little!) different when either variable changes. And now that I think about it, I should include
brand into the equation. String alloys, gauge and brand changes all have an effect on a guitar’s sound and responsiveness.
Changing blades in these RBSRs seems to have a similar effect.