I think the thing with Android is, as it is designed (or not) to run on so many varied pieces of hardware, it often NEEDS the little bits of tweeking to actually make it work properly unless you are using one of the Android flagship devices. So it has to be open source, how many devices work better on a CM version of Android as oppossed to the vanilla for instance?
I think Golfball hs nailed it though. It IS all about personal preference. I personally cannot be bothered with customising my phone. It is a thing, to be used until it breaks, and then I buy a new thing. I feel no connection to it, it gives me no pride of ownership and I do not feel any need to spend time making alterations to it.
When I got my first 3G I did as I was interested and jailbreaking the iPhone was fun. Androids live wallpapers are about the only customisation I find interesting now. I have absolutely no interest in linking my phones capabilities in with any social networking apps or sites, I don't use it as a developer, it is just a thing that I use to call people, take photos when I don't have my SLR, write emails, surf when I don't have a tab or laptop to hand, watch TV/Films, listen to music and to read a bit of news... IMO pretty much Android and iOS will allow you to do all of those to similar levels, so it just comes down to which I like and I like the iPhone better. Simple as that really, I just prefer the GUI on iOS and the handset is pretty solid. Got a 4G not far off coming up to it's 24 months and, having used a bumper on it the whole time, it is still in perfect nick.