NEWS: Movie Magic Conjured by Science
If you want the most selection, DVDs trounce streaming. Netflix has about 12,000 titles available for streaming (as estimated by a third-party site, Instantwatcher) but "more than 100,000" on disc (spokesman Steve Swasey wouldn't get more specific). Further, new titles take longer to show up in the streaming catalog than on disc - then vanish from it at arbitrary timetables.
For that, you can blame Hollywood's convoluted "release window" business model, which tries to maximize a movie's profits by artificially constraining its availability in particular distribution channels. (Were this post to be offered along those lines, first you might have to pay to hear me read it in person, then you could peruse it on your computer, and eventually you could purchase a print copy.)
But clicking a "Watch Now" button to view a movie over the Internet has a spontaneous convenience impossible with discs-by-mail. Further, those "watch now" buttons exist in a growing variety of living-room gadgets that connect to Netflix: HDTVs, Blu-ray players, TiVo digital video recorders, Apple TV and other streaming-media receivers, video-game consoles and smartphones and tablets.