Besides FRAM, one of the killer features in MSP430 is the clock demand feature. High frequency peripherals can request its clock while the part is in a sleep mode, so you can have A/D or SPI stuff running at a proportionally low power consumption (instead of largely offset by a continuously running HFOSC).
Now this feature has started to appear in many ARM parts: many modern SiLabs chips, STM32U5, etc.
In terms of CPU horsepower or efficiency, I think the MSP430 falls a bit behind for a while. STM32L4 used to be my previous favorite, with many oscillator settings thanks to its MSI at a fairly okay efficiency.
Now I've switched over to STM32U535, with DC/DC runs at 24MHz under 2mW. Its more a mid/high-end MCU with low power domain bolted on (like only a subset of peripherals support clock requests), though, but it manages fairly well nonetheless.