They're similar, in which they both can gain prowess and significantly reduce the ability accuracy of metal champs. However, they are pretty different from eachother. Red Magneto is a great damage and utility champ as he shuts down most abilities if the opponent is metal and he can gain lots of prowess for some huge special attack damage. White magneto on the other hand is more for support as his persistent charges will benefit other champs, such as giving passive stun parry to her champs when activated.
Comments
White mags is good for damage and very solid as support. As standalone champ he can pull his weight any day
Red mags: if you see any metal champ, and if there is no AAR protection node or ability, Red mags is always the answer