I have both as well and the Mirra 2, in my mind, is the way to go. For me, the Aeron has the edge of the seat part where the back of my thighs rest and it starts getting uncomfortable after 15 mins. The Mirra doesn't have this issue. The Mirra back also hugs my shoulder blades a little better. The plastic back of my Mirra doesn't bother me vs. the Aeron mesh.

I would recommend the Mirra for anyone looking at Aeron. They're usually cheaper too. I got my Mirra on Amazon for around $600 which the Aeron was going for, I think at the time, around $900.