Recently bought a GRX-equipped gravel bike and after lots of research will be using a stages left side PM.
My current road bike is a Canyon Endurace with Ultegra with a Stages PM. I used to swap the PM between my old gravel bike and road bike with no issue and used on the trainer. So 1 PM for all. I would like to do the same.
My thought was to get a 48/31 GRX 2x (and front mech) for the Endurace and replace the cassette with an 11-30 (currently has 50/34 11-34). Beyond PM swapping, I think this may be a better set up for the way I ride. I only lose slight top end, and gain smaller gaps in smaller cogs (which will make outside TR workouts easier), with the same climbing range. I don’t race fast crits, but do fondos/gravel races, etc… A few times a year I do some brutal mountain climbs with sections of 25% grades, steep gravel, and long climbs.
I know the q factor will be a little wider, but anything I am missing?