I can't offer any input on either the iphone 5 or galaxy offerings, but I wanted to throw windows phones into the mix....
I had an android phone for a few years, and had some issues with the software/os updates as the phone got older and the hardware wasn't so happy with the newer software. This might be better now, but it was a bummer. I also never "needed" to customize my phone that much, so that aspect of android wasn't that appealing.
When it was new phone time last spring, I ruled out the iphones right away (too much $$ and didn't want to change carriers) and wasn't thrilled at the prospect of android again (the old phone was REALLY laggy at that point, would miss calls, etc) so I played with a windows phone for a bit. It's fast, integrates fairly well with google (maps are via bing, but the physical maps seem ok and I'd rather look at a map than follow directions, so it works for me), and I'm really happy with it. If you can hold out until November, the windows 8 phones are coming out, but I'm perfectly happy with the current generation (which may also go on sale with the arrival of wp8). You do have to use microsoft's zune software to transfer files, so no itunes, but I have an ipod for music anyway and itunes/zune seem to play fairly well with the same music library, so no big deal.

