i'm going to guess that you could model a magnet as being made of units of magnetic-strength-with-mass and an electromagnet as being made of units of magnetic-strength-with-current and you'd basically want the smallest volume of the highest grade magnet, shape and distance unaddressed, to accelerate it with a given electromagnet. each magnet particle needing some number of electromagnet units to lift it.
electromagnetic seem to be sold based on a raw force, such as "holding force" . unsure what this force represents. alternatively one could wrap cores with wire by hand.
