[Coda]

Different radio interference on different channels. If it's affecting you differently, it could be something as simple as where you are in the house, or it could be something to do with the physical construction of your computers and where your wifi antennas are mounted. It could also be that one of you is running on 2.4GHz and the other is running on 5GHz, although most routers have the channel settings for the two bands controlled independently instead of together because they're completely unrelated. High-end routers are capable of operating on multiple channels simultaneously for just such a reason.