Uhm, reverse that... a 1.2 Ghz 970 draws less than 20 Watts, where the 1.2 Ghz G4 draws around 32 Watts (estimated). The 970 is a much better choice for laptops/etc. However, at the current max, a 1.4Ghz G4 seems to draw less power than a 1.8Ghz 970... so the G4 seems to be a better long-term choice for laptops (for now).
The IBM Blade servers are designed for are small systems that are made for clustering, and don't have a lot of space or airflow... cool chips are vital. Ironically, laptops and blades seem to have similar requirements in terms of power and heat.