The only real difference is that if there is a schedule change or cancellation in advance of travel you have to deal with Expedia. In my experience they are absolutely shocking at dealing with these sorts of things. I had a flight cancellation and they insisted I had to pay to change the date to cover the fare difference. Essentially their agents are not trained well, including their supervisors. It took me 6 calls over 5 weeks to get it sorted. So if you're not saving much money, don't bother.

N.B. The route I was on has 1 flight per day, so changing the date was the only option.