First of all, great overview!
The focus on the software development side is intentional I believe, but I feel that it is very important to also look at the hardware and hardware/firmware crossover point when judging a SDK.
Meaning - the ease of pin function planning and peripheral mapping to those pins and enabling required peripherals. For me, a very important metric is a following workflow: choose any MCU from the manufacturers lineup, configure it for your specific application and get to a compiling sample project with all peripheral set up (clocks, DMAs, interrupt handlers etc) ready for further tuning and application development.
For example, with STM32Cube, setting up a project with Ethernet, FreeRTOS, LWIP, DMA channels and couple of other communication busses is quite trivial. Would be really interesting how other manufacturers SDKs compare to that. For me, often, getting to the point where the MCU feature planning and setup is done is the most frustrating and error-prone part of the development process…