In Rick's France guidebook he lists the options for tours at the Orsay:
Tours: Audioguides cost €5. English guided tours usually run daily at 11:30 (€6/1.5 hours, none on Sun, tours may also run at 14:30--inquire when you arrive). Or you can download this chapter as a free Rick Steves audio tour (search your device's app store for "Rick Steves' Audio Europe" or visit http://www.ricksteves.com/watch-read-listen/audio/audio-tours/paris for the tour as a stand alone MP3 file).
I'd say whatever option you choose is a win. We really like the audio tours we've put together and they're free, so that's a plus. With Rick's audio tour, or a museum audio guide, you can skip around and go at your own leisure viewing the art, which I personally like. The Orsay houses some of the best Impressionist art you will find in Europe, so if this style is one of your favorites maybe doing a walking tour with a docent from the museum will give you more in depth insight. I'd say pick whichever of these options appeals to you most given your time and interests.