Retro whats the torque & load compared to those muscle memory actuators? or Pneumatic hydraulic servos?
Are the brushless dc motors compatible with an arduino? or do they need a special interface etc ?
Muscle memory actuators are not real powerful, but I guess you could parallel a lot of them and increase pulling power. I've only read of them mostly, although they were used as meter pointer movers in process controllers I have seen in a refinery.
Now Pneumatic actuators are the bad boys for actuator force, they can handle any load you can imagine. You just multiply the maximum air pressure you have available times the square inch area of the piston it's pushing against to get the force available. A 3" piston with 15 psi available will generate over 100 pounds of force.
And of course electric motors can come in any size required, limited only by your cubic dollars available. 
The speed controllers used with brushless motor are controlled just as if they were a servo, so an Arduino can drive them using the servo library.
Lefty