Cortex A8 was considered power hungry even for its time, among other 40nm chips.
Cortex A9 was both a more efficient and more powerful chip. Now, what most OEMs use in low-end phones, and even smartwatches is Cortex A7 which is roughly as powerful as Cortex A8, but far more efficient, both because of its design but also because it comes at 28nm.
It's really strange that Motorola would go for the 3 year old Cortex A8 core, when Cortex A7 has been available for more than a year, and several chip makers produce them in different varieties.
Cortex A9 was both a more efficient and more powerful chip. Now, what most OEMs use in low-end phones, and even smartwatches is Cortex A7 which is roughly as powerful as Cortex A8, but far more efficient, both because of its design but also because it comes at 28nm.
I think this comparison was made by ARM itself:
http://archive.linuxgizmos.com/ldimages/stories/arm_cortexa7...
It's really strange that Motorola would go for the 3 year old Cortex A8 core, when Cortex A7 has been available for more than a year, and several chip makers produce them in different varieties.