What is the difference between ARM [Cortex M7](http://www.arm.com/products/processors/cortex-m/cortex-m7-processor.php) [Cortex A53](http://www.arm.com/products/processors/cortex-a/cortex-a53-processor.php) (or A17)? Why one will choose one over the other? To what kind of applications does each of those is targeted for? Which one will be more suited (and why?) for wireless communications and video?