which .com to use for booking flight?
 

getting ready to book thanksgiving travel - have linked my accounts for status on both.

I know about using the ff account # for the airline operating the flight - but is there a preference for which website to use to book the flight?

Not really.

Though there is a difference in how change fees are handled between carriers (e.g., UA deducts the change fee from the ticket value, and CO charges the change fee as new money), so it's typically advantageous to book as UA coded though UA whenever possible, even if your flights are on CO metal.