I tried private browsing on Safari, but found that it would prevent auto-fill in cases such as auto-logon to forums like IPF (so you have to logon in each time), and would block some video. For instance, there's a video link in the forum to a tribute to Steve Jobs at a German Apple store; on private browsing, I could hear sound, but see no video on that link. PB had that effect in Safari, as well as Atomic. I didn't try my other browsers.
I don't need PB, but I was checking out features. If I wanted PB, I'd set it in an individual app, like Atomic, rather in iPad settings, because it wouldn't limit viewing functions on all browsers, just the app.