Spot on as always Johanna! I'd second the iTunes option as the primary method of updating. As Johanna pointed out, OTA would not require a computer to do so. However, note that if you perform an OTA update, you'll lose about 500MB or so of storage as iOS caches some of the older directories on your device, which is questionable since you're not allowed to downgrade your device, so those directories aren't needed anyways, so that'll be 500MB that you lost for pretty much nothing.
And as Johanna pointed out, using iTunes, you won't need to download the delta onto your device, so if you're tight on storage space, you won't have to worry about deleting a lot of data to make room for the delta (though updates will take up a bit more space so if you're at the brim, you'll still need to make some room). Plus you won't be forfeiting 500 MB for nothing, meaning 500MB that you'll actually get to keep and use for something practical.