Re: We should use neither
WIth regard to the comment that the Pi is only used for hobby, learning, prototyping, not commercial usage. This isn't true. There are upwards of a million Pi's out there being used in industrial applications. You just never hear about it.
If you add on those used as media boxes (ie, not for hobby, learning, prototyping, but as a black box that does a task etc), then the number is even larger.
One of the reasons they get used instead of custom PCB's is that the SoC is not available in low quantities, and the development costs of a custom PCB on small runs is MUCH higher than just using a Pi. Why bother with a custom board if the Pi already does what you want, with a solid Linux kernel and support.
It's also not a 'phone chip on a breakout board'. The original SoC (2835) was used in the Roku media stick, but never in a phone. The history of the chip line is available on line somewhere.