Android isn't a smartphone like the iPhone is. You can't just go to the store and ask for an "Android." What Android is, is an operating system that Google made, which manufacturers like Motorola and HTC can use to make smartphones and tablets. It's like the Windows of the smartphone world, except that it's made by Google instead of Microsoft.
By that comparison, then, the iPhone is like a Mac. And if you know anything about Macs versus PCs, you know what all that implies. Are you a Mac person or a PC person? If you already know the answer to that question, you already have an idea of which kind of phone you would like ... an iPhone made by Apple, or an Android phone made by any of a number of manufacturers.
If you don't know, how can you tell?
You might be a Mac/iPhone if ...
... you like the idea of a smartphone that doesn't just "Just Work," but works beautifully and leaves you feeling excited that you get to use it. This is an extremely subjective thing, and it sounds stupid to people who don't get it. The only way to find out if you're one of these people is by playing with an iPhone in person.
The iPhone has a somewhat wider appeal than its "artsy, creative" counterpart the Mac, however. Because unlike in the Mac/PC world -- where Macs have a handful of polished apps, while PCs have a whole slew of them plus nearly all the good games -- the iPhone dominates, software-wise. iPhone apps tend to look and work better than Android ones; even gamers choose iPhone over Android (although some game companies are choosing Android). You can see it in the old iPhone commercials, the ones that are all about the apps and how they work.
Just like how the iPad is the default "tablet" for most people, the iPhone has been the default smartphone for awhile now. More Android phones get sold than iPhones, but compared to any one carrier or manufacturer's flagship Android phone the iPhone still has a commanding lead. Because of that and the iPhone's app situation, if it fits with your lifestyle and carrier it should probably be your choice, too.
You might be a PC/Android if ...
There are ideological reasons why some people like Android phones. Most of these have to do with "openness," such as how Google publishes Android's "open-source" programming code online for anyone to use. You have to get Google's permission to use its apps, though, including the Android Market. So while Barnes and Noble (among others) has put that code to good use without needing Google's permission, Android isn't as open as some would have you believe.
In the Mac / PC world, most people choose PCs because of how cheap they are, or because they're used to PCs. The iPhone came out before Android phones, though, and it doesn't cost any more than an equivalent Android smartphone. So these advantages aren't there for Android, like they are for PCs.
Why would you want an Android phone, then? Unless open-source code is important to you, it comes down to feature requirements, plus personal taste and reasons that are just as subjective as why some people prefer Macs.
Ultimately, the choice isn't between "Android" and the iPhone; it's between the iPhone and every Android phone out there. If you find an Android phone you like better than the iPhone, like I did, go ahead and get it! And even if you don't, be glad you have the choice.
Jared Spurbeck is an open-source software enthusiast, who uses an Android phone and an Ubuntu laptop PC. He has been writing about technology and electronics since 2008.