Même Engadget, connu pour leur pro-applelisme, n'arrivent pas à répondre à cette question
http://www.engadget.com/2m/2011/10/14/iphone-4s-review/
Is this the best iPhone yet? Yes, of course it is. The iPhone 4S takes the previous king, gives it some more pep and adds on a better camera to boot, all without really gaining any extra weight. This is, then, the best iPhone on the market, but that still leaves us with two unanswered questions: is it the best phone on the market, and is it worth the upgrade?
The first question is hard to answer. If you're into iOS, have a wealth of App Store purchases you'd like to keep using and in general are down with the Apple ecosystem then, yes, this is the best phone out there. If, however, you've been shopping around, or are already tight with Android, Windows Phone, BlackBerry or Meego (hey, the N9 is pretty great) then it's hard to see this as a truly forward-looking device. The 3.5-inch display and abject lack of 4G connectivity alone make this phone feel a little too conservative to really tickle the fancy of those looking for something a bit more progressive.
So, then, is it worth the upgrade? Well, if your contract happens to be up and you want an iPhone and you haven't already jumped on the iPhone 4 then yes, this is the one you want. It does come at a $100 premium over its predecessor, but in the long run that premium will be worth it as the 4S will surely be supported by Apple for a good bit longer than the 4 (as the 3GS continues to be, while the 3G is now fading into obsolescence). But, if you're mid-contract or haven't quite yet been wooed by all that iOS has to offer, we'd recommend sitting this one out. The iPhone 4S does everything better than the iPhone 4, but it simply doesn't do anything substantially different.