There are also situations during irrops when the airline may rightly or wrongly declare something to be your TA's fault and tell you to deal with them.

Granted this has not happened to me for several years, but you'd avoid even the remote possibility if the airline itself sold the ticket.

So yes, everything else being equal, I'd buy from the airline. If not equal, I'd weigh the choices. For example if Orbitz/Expedia/Travelocity were throwing in some discount or hotel/car-rental deal that I could actually use, that may change my calculation.