The KF7 makes less noise on NTSC. The only 2 places where this makes a big diffrence is second "room", becouse if you use KF7 to kill guards on stairs here on PAL there's a lower chance of getting both upcoming doors opened than on NTSC. Also at the crate area you can start shooting as the door opens on NTSC while on PAL you have to start shooting later or else the guards opening door to Satellite room will warp the door.
I'm not sure if there are less guards "cloning" on ntsc too? But probably not.