[McP]

Power - how many Watts does it need? Speed - how quickly can it perform operations?

[wmf]

You can get low power with a simple design at a low clock. This definitely will not help achieve high performance later.

[weebull]

Clock rate isn't the only factor. A design can be power hungry at a low clock rate if designed badly, and if it it is... you're never getting that think running fast.