Try also thinking about this from the future perspective. I mean how much has android improved and innovated in the past 2 years compared to iOS change in 2 years? Android has become really fluent, cool, customizable (always been though

) iOS hasn't really changed to be honest.
I was serious iOS fan, had iphone 4 and 4S. I changed to galaxy s4 2 weeks ago and haven't missed anything (except tap the clock for top and photostreaming to my macbook. I love my s4 ( & android). So yes, I would say go with s4, it will pay off in the long run (especially in the future).
The next android version will propably be really cool and iOS7...well..propably not that cool except some visual improvements (flatter design). The iphone 5 is a really good phone too but keep the s4.

I think we will see really cool features with next android (4.3) so I bet you would feel bummed if you choose iphone 5, iOS7 will propably be disappointing (maybe not as much as iOS6)