An Iphone or an Android 2.2+ device (I have an HTC Inspire 4G) is the way to go. The iPhone still has the slicker looking UI, but I am preferential to the Android for the way it handles multi-tasking, and for a range of behind the scenes app development details you undoubtedly have no interest in.
As it stands today (to the best of my knowledge about the current version of iOS4), the android phones are much more tightly integrated into the larger Googleverse than iPhones.
Examples: Android phones receive over the air (OTA) software updates, while iPhones sync with iTunes. Google contacts, calendars, rss feeds, podcasts, google voice, pictures, etc. all sync tightly to the "cloud" from your Android device. You can use "Chrome to phone" to send websites from chrome wirelessly to you Android device. If you pick an app from the google app market on your laptop/desktop, it installs automatically to the phone. Android 2.2+ also includes native tethering/hotspot capability.
I'm fairly certain you can make an iPhone do most of the above, but I don't know how baked in these features are. Some Android apps are not near as polished as the iPhone counterparts, and their are still some weird UI quirks in Android 2.2. I eagerly await 2.3 for my phone.
One thing to not about the Android phones is that not all of the manufacturers skins over the OS are created equal. In my opinion they range from mediocre (Motorola) to pretty good (HTC). I personally would only consider android phones from HTC and Samsung at this point, but maybe the other Android manufacturers will improve their UI skins.