If you always buy J, it probably doesn't matter. If you live in California, sure, LAX-YWG might work well, but from SFO, I'm connecting no matter what.
I don't always buy J, but I always sit in J, which is not true of my many 1K/GS friends who fly UA out of SFO.
If you live in YYZ, and want status benefits, there's no other airline that will take you "anywhere".
But I agree with everything else.