|L to R: iPhone 4, iPhone 3GS, Nexus One|
After a month-long dalliance with Google's Nexus One mobile phone--which I did like but did not love--I re-entered the Apple fold and signed a two-year contract for an iPhone 4. The Nexus had superior hardware to the two-year-old iPhone 3G that it replaced but in my humble opinion wasn't quite up to the i4. The fact that I prefer Apple's IOS4 operating system to Google's Android only made the decision easier.
Another disincentive to switch from Apple is that I had dollars invested in Apple's iTunes music, videos, and Applications. (I understand that there are solutions to converting from iTunes to Android and vice versa without losing my investment, but I didn't want to go through the hassle.)
All that said, if I were starting anew, I might well pick an Android phone like the Nexus One. I like the use of the "cloud", i.e., one can update one's calendar or address book in gmail, and all one's computers and mobile devices automatically have access to the new data on Google's servers. Also, the fact that web videos written in Flash cannot be viewed in the iPhone is somewhat irritating.
There are numerous mobile-product comparisons. Below is Gizmodo's: