I did some comparison between rmc and rmc3 (in .325 and picco).
I hate the looks of the weird bumper in the safety version, but my opinion is that for most cutting the difference is negligible. The bumper is only involved at all in certain tip cutting operations like boring.
But even with the stihl low kickback chain, I can bore easily - even engrain.
So my opinion is that the difference is no big deal. I prefer the non "safety" version where it's available to me (like in the 63pcm) but on the .050 semi chisel .325 where I can't get a non reduced kickback stihl I use the 3 version no problem.
The only question in my mind is how the low kickback version is when the cutters are worn down a lot, and the depth gauges are shortened accordingly. But at the same time, the extra bumber gets ground away when sharpening anyway (it's in the gullet) so I don't know if it matters.
So it is not the common view, but I say in the stihl .325 and picco anyway, the difference between the low and high kickback vesions is small with a sharp chain. In fact in reality I don't find it reduces kickback much either.
It may also depend on how the chain is sharpened, as I try to keep the original amount of hook to the limits of my grinder. (In looking at others' chains commonly I see chains not really sharp and too much hook.)
Before I get beat up by those that look down on using a grinder, I will say on the smaller cutters like lp, 1/4 and even .325 (which is a slight bigger cutter on stihl chain) the difference in cutting between ground and files is minimal (don't know why exactly). On 3/8 filed chain clearly cuts better than ground on my 510.
But I seldom use round 3/8 once I got my ProSharp a number of years ago - square all the way baby on 3/8.