I've had an Android phone for 3 days and it's amazingly better than the iTouch 4 I've had for months. Seriously, the iTouch was my first device of this sort, and while I can't comment on hwo it works with calls and texts, the interface for the non-phone stuff is the same anyway.
Android kicks iOS' ass in all respects when it comes to customization. The built-in software is garbage sometimes but people's apps can do amazing things. iOS doesn't let apps put widgets on your home menu, just their icons and occasionally some little tidbits of info on the icon, but that's it. Icons are always 1x1 square on the grid, and never bigger. I just discovered widgets on my Xperia Play and I'm loving them.

Beyond that, the interface in general. Drag down from the top to bring up your notifications? YES, please! Buttons on the bottom letting you return to the main screen, bring up a context-sensitive settings list, back out of your current page, or even bring up a Google search at the click of a single button? How did I ever live without all that? I mean, hell, the iTouch couldn't even get ONE button right. It managed to count one click as two quite often, and that got really annoying.
Android is a little spread out and a little more DIY than iOS, but it's still incredibly easy if you get some help from Google. Nothing is hard to do but finding out how to do it can be the tough part.
But back to the main topic, customization. iOS doesn't let you change the look of the interface at all. Android lets you screw with it however you feel like. iOS requires all apps to be checked and approved for the one and only app market for the device. Android is completely open and unrestricted, to any number of markets. Apple sticks you to one piece of hardware, complicating it with a bunch of iterations of that hardware. Android is, again, completely open. How you can possibly think iOS is more customizable, ESPECIALLY when you're just talking about the BACKGROUND COLOR of a single built-in app.