I hate playing second fiddle to my companion, so ~if~ I give them a weapon it certainly won't be a great one, and definitely won't be an explosive one (even a shotgun, if it has 'spread' to the blast). If I ~do~ use a companion, I pretty much want it there to talk to me, to comment on the world, to haul my stuff around. It wouldn't hurt if they could fight, but I certainly wouldn't go out of my way to make them even ~better~ at fighting (feel insecure enough when they instantly spin to attack foes while I try to find where the gunfire is coming from).... so I can't see the utility in this perk (for me, anyway).
I'd be tempted to use the Lone Wanderer perk (damage resistance and carry capacity without a Companion) but I ~do~ enjoy talking to companions (if they are done right) and I'm sure the extra carry capacity of a Companion is greater than the little bit extra the Lone Wanderer perk gives me. I just don't want a ~combat~ companion, really.