The faster chipram speed is not measured in nanoseconds. It's measured in "timeslots per raster line": There are twice as many of those time slots on the Amiga Reloaded, which is the reason for the higher performance.
FastRAM will always be faster, as it's tied more closely to the CPU, and it doesn't have to wait for a full timeslot. On Fastmem with no other than the CPU being the bus master, an access can be started any time. Chipram on the other side requires time scheduling: Even if the CPU starts an access within a free time slot, the scheduler may not start the access, because there's the next access from a DMA channel scheduled before the CPU access can be finished/closed.
C2P routines will benefit. Old games either won't see a difference, or they will show funny (=unwanted) effects, which is why you can configure these additional time slots as "available or not" before you start such an old program (useful for WHDload games - no re-boot required).