Is the convention of dual core being more efficient than quad a misnomer?

Case in point, the 2410 and 2430 are dual cores, but appear to get just as hot as the 2630 and 2670. Battery life also seems just as challenged. I appreciate duals are 35W vs 45W TDP, but those are thresholds and not indicative of actual power used unless very heavy computational or decoding tasks. At that point, the bottleneck of the dual kicks in and is constained, but it would be impractical to use for those functions on battery anyway.

Seems for most tasks, both core designs are on par (or quad is better), so people assuming less heat and better battery life with dual cores may be assuming wrong. I am/was one of those apparent assumers.

 

Based on tech reading and discussing with some techs, it does appear to be a misnomer.