MSP430's aren't trying to be energy efficient per operation - they are really bad at processing. What they are good at is running complex circuits/peripherals at a low total energy consumption over a long time.
The fact that they're running at 8Mhz is telling... that's far from the "low power" level. As far as I recall, you generally run using internal low-frequency RC oscillator for low power, and then just boot up the high speed crystal oscillator if you really need it.