Thanks for the information guys. It will be on a Canadian passport. Generally I haven't had a problem flying within the US our out of the US with a Canadian passport. I haven't noticed any difference when compared to colleagues with US passports. When flying out of Toronto we have US customs at the Toronto airport, so there's no customs on arrival (we come in like a domestic flight).

Expedia turns out to be the cheapest once factoring in US dollar exchange rates. That's because Expedia.ca charges in Canadian dollars and has a better rate (which they don't mention) than my bank or credit card company. If I paid in US, the rate would just negate the small savings in base price.

However, I'm glad I did check out the other sites, especially Kayak. It makes searching other places a breeze because of its superior UI and seemingly thorough digging. Using it and checking Orbitz site also lead me to find out that United doesn't serve any food for free nor do they allow any checked baggage for free. That's something I appreciate knowing in advance.