What can the iPhone 5 do that other iPhones can't?

Got iPhone 5 for christmas

Be taller

Well it has LTE!

Facetime without Wi-Fi, lte (4g), turn by turn navigation with voice guidance

and other stuff but thats what I remember

It is always better to keep your iPhone 5. Apple is good at giving free updates that improve your phone functionality. But they are discounting the features on older iphone. Like facetime in iphone 4 can only be in Wi-Fi, it gets no siri, it doesn't get apple flyover map feature.
and even right now i don't see much difference in features, and happily keep using my iphone 4, i know, having the most recent will give you better/ longer updates from apple.

i especially valued my iphone 4 got an update to iMessage, so i don't have to pay to text now. All over the world. Its update like this that you won't see initially, but blow you away.

when i bought my iphone 4 i don't have Photostream, and been thinking on sharing photos to my family, and luckily i got the update and now i can share group specific albums.

and we have not even consider App store support.

don't think on replacing with older model unless you need the money more.