In Figure 12, you can see a power consumption comparison between C7-M, Pentium M and Celeron M. According to this data, at 1.5 GHz, VIA C7-M dissipates 12 W, while Pentium M dissipates 21 W and Celeron M dissipates 24.5 W. At 1.8 GHz, C7-M dissipates 15 W while Pentium M dissipates 27 W.
As for performance, VIA published the data shown in Figure 13, making a “performance/watt” comparison. Really interesting, but… beware! This data talks about a ratio, not about absolute values…
A final comparison table can be seen in Figure 15.