Normally I'd say M0+ is the king and offers good debug facilities over the M0 despite the slightly larger die size.
However, @rurban is probably correct purely because Ambiq is building their portfolio around the M4 (and M33), and they seem to be working hardest in pursuing and patenting IoT layouts/technologies that reduce energy usage.
I love AVR for teaching/learning, but the fact that you can* get a more powerful, larger memory Cortex-M at a much lower cost than, say, an Atmega... I don't know why anyone would choose AVR for a new design outside of niche uses.
I love it all. Cortex-M0, M3, M4, M7, and A7 all together span several full orders of magnitude in performance. Every one of them has their niche. Unfortunately for ARM, all of those designs are many years old and they are still nearly optimal in their niches. ARMv8-M parts are starting to show up, but they aren't exactly revolutionary compared to their predecessors.
they're all a decade old. it's absurd that we havent found any architectural wins.
i have no idea whether there'a just scant dew wins to be had, or whether this complete lack of innovation is a company asleep at the wheel.
do you also love the cortex-a53 for application processing? because it too is another dinosaur relic that we seemingly cant eacape from. a55 seems to have made a like 12% difference.
As an EE/embedded dev the M4s are approaching a mature technology for the bog standard MCU driven products I work on. You can get a 180MHz processor with 1MB of RAM and 2MB of flash. For reading sensors and doing some lightweight application layer stuff I don’t know what more I would even ask for. Current product is not power constrained so not paying much attention to that.
However, @rurban is probably correct purely because Ambiq is building their portfolio around the M4 (and M33), and they seem to be working hardest in pursuing and patenting IoT layouts/technologies that reduce energy usage.
I love AVR for teaching/learning, but the fact that you can* get a more powerful, larger memory Cortex-M at a much lower cost than, say, an Atmega... I don't know why anyone would choose AVR for a new design outside of niche uses.
(* - pre-2020)