There are no real benifits you will notice. Noise will be slightly more. Its illegal to run a decat, so if stopped can be looking at a fine etc. Sensors should be okay as only one before CAT.
Upto you at end of day, a bit of pipe and a sleeve will fo the same as a jetex decat, but Jetex is high qualaty.
MOTs will also be a pain as its a fail without a CAT