Missiles are slow in comparison to rail guns, hence small non explosive payload vs high explosive, with guidence. To dodge something means seeing it, calculating trajectory, and using that information. We don't have the tech at reasonable distance to do that with something hyper sonic workout a lot of distance. The realitive small size of the projectile from a rail gun complicates this. Also dodging missiles rare outside movies, that's why fighters use radar jamming, stealth, flares, chaff to confuse their guidence.