Go Fontyyy......
Just to expand on this slightly. The 28R forks are crap...nuff said about them. The 28SE forks have the slotted brass adjusters and control low speed rebound damping by changing the flow rate at the top of the damper rod. They also have a very small effect on low speed compression damping.
The 28SP has the adjuster valve fitted right down deep and is linked to the funky blue adjusters by an alloy rod inside the damper rod. Mainly adjusts low speed rebound damping. Also has a small effect on low speed compression damping, but more so than the SE (and MC21SP) type.