With the exception of US and China 5.8 is less power than 2.4 -and- as you have said 5.8 suffers more than 2.4 with propagation attenuation. Even the atmosphere will average 7+dB loss at 5.8 (compared to 2.4) in LOS conditions. Only advantage for 5.8 is in crowded RF environments.2.4 doesn't necessarily have more power, but being at a lower frequency it is less attenuated with obstructions.