CP is at a disadvantage compared to mainline AS (or even DL) flights. First, if the weather craps out, those planes get even more delayed and they seem to have more mechanical problems. My last flight with them was delayed almost 12 hours. Luckily, I was put on an AS flight instead.
So, if you are looking for reliability to SJC, I would go with AS. But, as others have mentioned, flying AS's partners on international routes does not get you the same benefits as you would with DL's partners (or UA and AA) either. But, as an FO, the benefits aren't really worth staying around for IMO.