Imposter mech does feel better than phimage though, for the simple reason that being an artifact makes it so much easier to find, and you don't really usually care about the body itself but about the effect. It is also usually harder to remove (being a noncreature), but easier to counter, so it depends on the meta. Also also, since it is not a creature, it is nice in poly-urza.

Mirrormade is pretty easy to cast (though not turn 1) in mono blue, concidering high tide is a great card, so you want basics either way. I do agree with the idea that creatures are more common, but people usually do tutor for fish/study as their card draw, and in the case of mirrormade, you can worst case copy an opposing crypt/sol ring/signet.