The 34 is indeed a little less rigid, but better damped is subjective and situational. Head to head the 34 gives more control over damping and progressiveness than the SID. Particularly because of how progressive the SID is base.RS overall makes better suspension than Fox. RS components are more rigid and better damped in every category.
The issue seems to be the SID's reliability, not it's performance.
Ultimately the SID is a DC fork, that's get treated like an Enduro fork by a large % of it's users as the Spur is so capable, and I suspect we are seeing the results of that.
I’m using ~same travel on the 34 but not hitting the progressive bottom which in repeated hits gets brutal on the SID. I consider my riding almost exclusively trail, I found the bottom of the SID once. At 120 mm riding trail I want to use that, not hit a progressive bottom at 90 mm. Or at least have more control over the bottom.