I am more of a fan of learning chord shapes independently of changing to other chords. That seems to me to be the more useful way of doing it. An Em is an Em is an Em no matter what comes before or after.

I don't think that answers your question, but just throwing that in. I use middle and ring for Em for the same reasons you mention. Also because open Em happens on the second fret and my index finger isn't allowed on the second fret, LOL!