While I wouldn't mind if Netflix would start offering a la carte as well, personally it's not much of a bother. The videos play either way.
So the whole "vs" approach may not be the most accurate. I'm not limited to any one of them, and with a month of Netflix costing less than a single top-tier movie "purchase" on iTunes it's not hard to justify a bit of mix and match.
Joking aside: Comparing only movies really skews the quality focus of the marketplaces to purchasers vice subscribers. Subscribers would be more motivated/less inhibited to watch TV series and would receive better value, than a purchaser. If that is true then iTunes would have a greater motivation to drive quality movies instead of series, and Netflix would have the inverse motivation.
I guess my point was that less arbitrary categorization would be a more accurate study. Delivery, Audience, Length, and Top Level Genres may provide more insight into the comparability of the 2 libraries.
1. Netflix doesn't get to choose what they can offer; the studios still dictate to them, and many times I know I can't find something just because some executive has a hair up his ass about "release dates".
2. You're assuming that popular == good.
http://www.fastcompany.com/1830524/the-juiced-misleading-siz...
The point is, even if Netflix did offer 100,000 titles, would they offer any more of the most popular films? I'll be running the numbers against Amazon prime and Lovefilm soon, so we'll see how they compare.