This report from 2016 puts NXP at twice the marketshare over STmicro who are sitting steadily in the fifth place:

https://epsnews.com/2017/05/01/nxp-tops-microcontroller-supp...

Although at least part of the sales volume difference can be explained by NXP having had more expensive i.MX range available (and others), so in terms of chips sold they might be closer to each other.

> This combined A7+M4 device is unusual

I'm not sure if I'd say that, previously NXP did the exact same thing with i.MX7, and TI with their AM5x. And of course don't forget the classic AM3x which had PRUs filling part of the same role.

To be fair that is largely because they aqquired Freescale, the year before they had almost the same market share.

And before that, they had their Vybrid line that's a A5 paired with an M4.

Didn't mean they're an underdog as such, one can still be up the top and push hard. Many just don't.

> the things you mention are pretty much par for the course

As I said my background was Arduino, and the ARM offering from Atmel is a lot more expensive from what I can gather. I don't know too much about the others. Coming from the Arduino, the peripherals of most STM32s are something else.

edit: of course the price point is also a big factor in this, with the "Blue Pill" and similar dev boars in the <$2 delivered range.