I am literally never asked if it is better to buy an Android tablet or an iPad. Nevertheless I will provide my opinion as though it matters because this is the Internet.
It is better to buy an iPad unless you have a bunch of Android apps you already bought that you want to use, in which case why are you even reading this? I say bought because many free Android apps are also free on iPad.
On both platforms it is important to be running the latest operating system if you want to use apps from the store. I have often followed a link from the web to the Android store only to be informed that the app I wanted is not available to me because I have an old version of Android. The worst thing to be told I couldn’t have was Google Chrome: the Android 3.2 browser was terrible.
On iPad this has never happened to me, in no small part because everyone whose device will run it gets each OS update at the same time. On Android the process is different: Google make a release, then your device manufacturer makes a release based on that, and finally your carrier makes a release based on that and makes it available to you. If you have a tablet without a cellular antenna you are spared this final step.
I have a WiFi-only Motorola Xoom 2, and I was first able to install Android 4.0.x last week. Google made it available almost a year earlier; given there was no carrier for me to wait for this seems to me to be an inexcusable delay.
Additionally, I find some of the UI idioms on Android tablets quite stupid in comparison to iOS. Worst is the universal ‘back’ button, which takes you to a random place you have been before. It is inexcusably inconsistent. It is also does not take the opportunity to tell you what it will do: perhaps on a 3.5-inch phone you couldn’t fit that on the screen but for sure you could on this 10-inch tablet.
Another for the list is the relative positioning of the keyboard and notifications. As I was typing the previous paragraph I received an email and the notification appeared over the letter I was about to tap: I ended up looking at my inbox and wondering what the hell had just happened.