this is the big one for battery-powered applications NRF52840 is specified to use 1.5uA when deep sleeping with RTC wake-up, while esp32-c3 is 5uA, which sound

this is the big one for battery-powered applications NRF52840 is specified to use 1.5uA when deep sleeping with RTC wake-up, while esp32-c3 is 5uA, which sounds ok, but is not the whole story. If you try to build something low-power with ESP32 you'll find that it takes a lot of time and energy to go from deep sleep to being able to transmit, while the NRF SDK is designed with that in mind. The NRF current consumption also includes the built-in voltage regulators -- this works from 1.7v to 5.5v, with a regulated output for peripherals, so all it needs is a battery and some passives. On the other hand the ESP32 is much more awkward -- it needs 3-3.6v, so you're going to need an external regulator, and a LDO with the required 500mA output current is going to have a significant quiescent current, and even then the voltages are awkward for lithium batteries once you consider the drop-out voltage. The tl;dr is that it's easy to get multiple years out of a coin cell with an NRF-based sensor, and that's just not happening with any ESP32.