But either way you'll need to collect bags in YYZ.
That I know. It's just with AC I am able to check in 3 bags, by AA only 1. So I want to make sure AC can check them all the way through and I won't need to pay AA excessive baggage fees.
ETA: A bit off topic, which one of these would you choose.
Air Canada TLV-YYZ (767) YYZ-ORD in economy (UA Miles)
or TLV-FRA (LY)-FRA-PHL (US)-PHL-ORD (AA) (Business class)
I don't really care so much about business more than economy. Its just a matter of convenience and airlines.