Train with whichever PM you will do your A race on, if that event involves hitting power targets consistently.
Examples of races in which the number on your PM is important: any triathlon, grand fondos, hilly road races, XCO, XCM, gravel, enduro.
Examples of races in which the number on your PM is not important: crits, CX, DH, BMX, tracklocross (I just threw that one in because I like the name).