I played bass guitar in bands for many years and my choice was multiple 10" speakers over 12" or 15". Smaller speakers can pump as much bass and air as bigger speakers but you need more of them. They tend to have a much better midrange response than bigger speakers.

Your main consideration is the distance over which you wish to project the sound. 15" have good bass response but only over a long distance. It takes a lot for the wave from a 15" to develop. They are not so good for personal stage monitoring which is why I liked 4 x 10" for bass onstage which was very punchy onstage but didn't throw so far that it would interfere with the front of house PA mix.

But if the speakers are your main source of audio for your performance then 15" will fill a room well.