The Mirage isn't out yet, so there are no real world numbers for efficiency.

If you're considering the Celerio, might as well consider the Eon. The Eon has more legroom, headroom and cargo space than the Celerio.

Fuel efficiency:
1. Eon
2. Celerio
3. Spark 1.0
4. Picanto 1.0

Space:
1. Picanto/Spark - huge interiors.
2. Eon - Only thing lacking is elbow room.
3. Celerio - seriously, the only thing the Celerio has is elbow room. The rear seats have no headroom or legroom compared to the Eon.

Features:
1. Picanto
2. Everyone else

Safety: They're all about the same.