The advantage of ther ST1100P is that they were fitted with the 40 Amp alternator right from the start, civvie versions had the 26 Amp alternator until 1996 (probably some still sold with the 26 Amp alternator as 97 models).
The 40 Amp alternator is just a little sturdier, especially if you're fitting spots, sirens, flashing lights and a heavy duty radio system.
They do have the bigger right hand bar switch block on them, nothing works, and they have the original Police wire loom taped off under the seat.