Seems the consensus is that Apple doesn't upgrade their devices enough each year....
I still really don't understand this sentiment.
IF rumors are true, the 5S will have a dual LED flash, 12MP camera, fingerprint sensor, the standard twice as fast and same if not better battery life.
What upgrades get put into Android flagships that are larger upgrades than this? As far as I could tell, the difference between the GS3 and GS4 was a bunch of software stuff, a better camera, faster processor and the same .5" screen increase people claim doesn't matter with the iPhone 4S -> 5.
Genuinely curious where this double standard comes from. Higher expectations of Apple? Seriously, consumers need to get a grip on reality. Flagships nowadays do everything 99% of consumers need them to do and MORE. These types of updates are what should be expected from ALL manufacturers at this point.
The smartphone has entered a state of maturity. Expecting the next iPhone (or Galaxy S phone) to cook you breakfast in the morning is absurd. And a bunch of these new features are software based anyway and have nothing to do with the actual phone release (iOS 7 will bring a boatload of new features).
As for the OP's original question, you have to decide for yourself. Do you want the larger screen? What other Apple products do you use? What Apple services do you use? Do you want to switch? What about your friends and family? Do they use iPhones or Android phones?
Ultimately, it comes down to each person's preference. You really can't go wrong with any of the flagships these days. Don't listen to people who tell you "x phone NEVER lags" or "y phone is so laggy". 9 times out of 10 its *************. Every phone will lag at some point. No smartphone (or piece of technology that exists) runs without a hiccup 100% of the time. Both the iPhone 5 and GS4 will run plenty well for you I'm sure. Both animate differently, which is something you should try out on each to see which you prefer (swiping through screens, typing on the keyboard, selecting an app, etc).
Anyways.....just my $0.02.