# Power in a frequency band: Spectral estimation versus time domain

I wish to find total power in a given frequency band within different time windows of a signal.

I see two methods of doing so, first in the frequency domain. One could estimate the power spectral density within the windows (i.e. tapering and then apply FFT), and integrate over the frequency band of interest.

In the time domain, one could apply a bandpass filter to the whole signal, and then estimate power as the mean square of the signal within the windows.

What would be the differences between the results of the two methods, could one of them be considered superior in this case?