You're flying from IAH, right? Definitely take the non-stops on CO both ways.

For outbound, a non-stop IAH-LHR gives you just enough time to rest and sleep. A connection on the E. Coast basically guarantees you'll spend the next day in London like a zombie as you can't get enough sleep on the short red-eye from E. Coast to London.

On the way back, you also want the non-stop because that means you won't need to redeposit bags and reclear security at an intermediate airport. Just fly straight back to IAH. Go through immigration, claim bags, customs and you're out of Terminal E going home.

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BTW, no pat-down for me at YVR when I flew HKG-YVR-LAX in January this year. So, not exactly the same procedure at various Canadian airports.