Also substantially more expensive, especially compared to the likes of the banana pi zero, which gets you four cores at 1.2Ghz, 512MB RAM, Linux and a GPU for 35% cheaper. Pair that with a Blue Pill STM32 for $3 if you need realtime and you still have money left over.
Marginally. The STM32H7 series offers Cortex-M7 cores at up to 480 MHz, with a Cortex-M4 coprocessor on some parts at 240 MHz. It's not quite as fast as the i.MXRT1052, but it's damn close.
The posted coremark scores do not support your claim that NXP iMXRT1062 is substantially more powerful. If I take these numbers at face value, then STM32 promises up to 45% more perf.