Is it worth replacing Kelsey Hayes 4 piston

Is the performance any better with SSBC calipers ? If not it's not worth it ,

The only performance change you will see using those SSBC calipers is a severe WALLET weight loss.

The disc brake effective swept area is the SAME - so you will not improve your braking stopping distance, just swapping in the SSBC calipers.

But you will lighten your wallet!