Extra price is the future shock
Comp has the FS 3.2
105 has the FS 3.1
Difference I believe is the 3.2 can be adjusted by hand. 3.1 needs springs swapped
I have the 1.5 which is the older model 3.1. It’s perfect, I have the stiffest spring.
I don’t think you need on the fly adjustments for a road bike. A gravel bike for sure depends on terrain.