What make the play better for a fhz spr kit or recessing?
It depends …
What is it you are trying to do? They are different and have different effects. The recessing will allow you to use sili response. From my recollection, the only purpose of an SPR in a FHZ is to use a different sized bearing.
I have a FHZ that’s been silicone recessed. I think this really is an ideal modification for the FHZ.
As far as an SPR, I might like that in a FHZ so I could have a C-sized bearing in there and compare how it plays.
The two mods are different, but can be complimentary. If you want a C-sized bearing in there, then use an SPR system or maybe even YYF spacers for their plastics. Then silicone recess it.