4 pistons isn't necessarily more powerful than 2. Its the same lever, so the force is distrusted over a greater area, which means less pressure and less friction.
Absolutely correct , forgetting about the XT brakes as far as im concerned .
HOPE tech M4 have 4 pistons , the even more powerful tech hope V2 are a slightly heavier option , they have 2 massive pistons that are aimed at the serious downhill/freeride market. I was tossing up over the M4 and V2 but the M4 was the happy medium.
Also when i got the M4 i shortened the hoses myself for the first time ever messing with hydraulic brakes in 1 hour with nothing but a few common tools and a 100ml bottle of DOT5.1
Bloody awesome brakes , im my opinion there is no comparison between hope and XT as i have said already above.
V2 - 2 massive pistons , downhill/freeride brakes
M4 - 4 pistons , AM/freeride brakes
Pic of mine with tech M4 brakes
Honestly , there is no point getting big brakes if you dont need them , i tossed up over a FR bike , but AM was best suited to me , same with your brakes , get what you need , there is a very slight weight difference over M4 v XT but the floating rotors and braided hoses aren't just for show ! braided hoses are more responsive , stops the elastic effect , floating rotors are lighter and disappate heat alot better.