Honest answer: probably not enough to justify the cost of switching so soon.
The M2S is genuinely impressive on paper, 1,500W peak, 150Nm, helical gears that kill the rattle, and 41% less drag when unpowered. But you're on an M1, which already puts out a measured 1,000W peak on the dyno and 120Nm boost. In practice, on trail, that gap is going to show up in a narrow set of situations: very sustained steep climbing, or moments where you need explosive torque at low cadence. For most riding, the M1 is already more motor than you'll ever use.
The other thing worth knowing:
@perry311079 confirmed
Amflow themselves have said the M1 is not compatible with an M2S upgrade, so it's not a retrofit situation. If you want the M2S you're buying a new bike, which puts you into PX Carbon territory at £6,499 rather than a simple motor swap.
Given you're less than a year in, the PL Carbon Pro is still a seriously capable machine. If the M1 isn't leaving you wanting on climbs or in turbo, there's no compelling reason to move yet. If you're regularly hitting the ceiling of what the motor can do, that's a different conversation.