I book with the airline when I want to gather frequent flyer points, which is most of the time. I then use those points on flat bed seats to Europe, which helps with jet lag. (Avoid Condor Air; most of their flat bed seats are broken)
Does the quote from Expedia include luggage, seat choice, cancellation? Those are pretty important. I have made several bookings through Expedia that were not fully flexible, and they could not be changed on line. I had to call them. This involved their call center in the Philippines (I asked because I could hear roosters crowing) and the agent was very courteous but couldn't answer any of my questions without first consulting their supervisor. It took hours. So now, on Expedia, I go for fully flexible fares.
I really like Expedia. We were scheduled to fly out of Venice a few years ago and many flights were suddenly cancelled due to a strike. I received a text notice about it that morning from Expedia, so we were prepared for the news when we arrived at the airport. I saw huge lines of people trying to rebook their flight. Then I received another text, saying they'd already re-booked us, leaving later in the day. We were able to check our bags and then return for a few more glorious hours in Venice without any worries or line waits.
I like using Expedia for hotels, as all the reservations are on one website. Otherwise, I tend to forget and book myself into two places at once, LOL. I gather Expedia points this way as well.
Have fun! You are going at a perfect time for weather and have a lovely itinerary planned.