Is the fact that the T3 does "only" 720p while the iPhone does 1080p the reason you label the iPhone's video capabilities as "vastly superior"? If so, that's a load of rubbish. 1080p video off a cell phone is so massively compressed it's NOWHERE near as good as what you get from even an entry level DSLR. I've seen the 1080p video out of an iPhone. It's good, but it's blown away from the 720p and 1080p I get from my DSLRs (and even P&Ss). And that's in good light. Drop the light and any smartphone's video will be a mess of compression artefacts and digital noise from having such a small sensor.
The iphone has a much more capable processor inside of it, which is why it does higher frame rates than the 100D, let alone t3. Apple also doesn't to worry about nerfing the IQ in order to maintain product differentiation.
To sum up, iPhone has better screen, better audio, and better at handling low light noise. And I'm pretty sure that was comparing to iPhone 5.
For the record. I'm not an Apple fan at all. I have a windows phone!