We'll be flying from Paris (staying near Musee D'Orsay in the 7th) to Barcelona and have a choice of two mid-day flights. One is an EasyJet flight that leaves from Orly, and the other Vueling from CDG. They are essentially the same price, and leave an hour apart from each other. Wondering whether one airport or airline is preferable over the other in terms of easy to get to/through, on-time records, etc. Any thoughts?

Man, if you can use Orly - go for it! CDG is best avoided whenever possible.

Orly is closer if you decide to take a taxi.
Or there is a bus from Denfert Rochereau (Orlybus).

Most Parisians prefer Orly.

I recommend Orly. It's easier to get to and definitely easier to find your way once there because it is a smaller airport.

Orly for sure and I have flown both airlines and think Easy Jet is more reliable.

Definitely Orly. The metro goes to both airports, and right into Orly.

The RER does n ot go directly to Orly. You must switch to an Airtrain for the last 10 minutes. But it is very easy to do. I would recommend the bus from Denfert-Rochereau if using public transportation. It might take longer than the RER but it has the convenience of one less transfer.

The metro goes neither to Roissy, nor to Orly (trains go to Roissy) but, while Orly is slightly more complicate to reach by public transports (minimum 1 exchange train + VAL or bus + VAL), it is still very doable (and a the taxi will be cheaper for Orly than Roissy)

And the rather big EasyJet (close from a 'normal' air carrier) has a better reputation than the smaller Vueling.

If you haven't made up your mind quite yet on Orly, I'll go ahead and add one more in favor. We recently returned from a trip that had us in and out of both airports - and Orly seemed to be the easiest to get in and out of. Public transport was easy, even with having to get off at one stop.

The RER C from Musée d'Orsay can take you to Pont de Rungis, from which there is a free shuttle bus to Orly.

Orly it is! Thanks everyone for all the great input. Kerouac, about how long does the RER/shuttle trip take?

CDG is much bigger and handles the bulk (if not all) of the overseas international flights. I would fly out of Orly! EasyJet is a frequent operator throughout Europe and is a reliable airline to take. Bon voyage!

The RER C + shuttle is not a fast trip, because there are no non-stop trains. The train stops everywhere. The shuttle bus part is quite rapid, because the buses to Orly Sud and Orly Ouest are waiting for the train.
The stop before Pont de Rungis is Orly-Ville and please note all of the signs that say "Airport Next Stop!" on the platform.