The COSETI Observatory
Electromagnetic SETI on planet Earth today is really about the passive detection of attention-getting beacon signals that may be aimed in our direction by ETIs located in our sector of the Milky Way Galaxy.
Little consideration and attention has been given to the detection of wideband data channels that ETIs may also transmit, and which may be co-located with the beacon signals.
What really matters is the signal-to-noise ratio at the receiver - which may be maximized in a noisier region of the electromagnetic spectrum because that is where the gain of the antenna can be optimized. It is too simplistic to suggest that ETIs would choose the quietest region of the spectrum to send their signals.