It was my understanding that Shimano's Servo brakes all generally had the same amount of power. Only the more expensive ones, SLX and XT, XTR had different upgrades for cooling and adjustment features.

I agree with others, rotor size does make a difference. Although, you can have a 203 rotor that while helps you stop nicely, if it's an affordable priced rotor, will need to be straightened or (forgot terminology) since some larger cheap rotors require constant maintenance (Shimano RT30's). Inexpensive rotors also only accept resin pads in case there is any future desire for metallic pads.

I remember watching the video below, thought it might be interesting here as well, but not sure if you ride like this and it might not pertain to OP.