I have answered this question a few times and honestly, never mind talking about it. I have owned both an iPad as well as an Android tablet. I have also had an iPod Touch and own a Samsung Droid Charge cell phone.
Both platforms are extremely robust and offer a wide variety of features. I do have a personal preference though which is what I believe it boils down to.
In the end, I chose the Android tablet (Asus Transformer TF101) because the iPad was limited as to what it could do for me in the technology field for work. I do alot of Windows system administration for work and the iPad does not offer the tools that I need to to my work remotely while the Android tablet does. Another reason that I chose the Android tablet is because of Adobe Flash Player support. Our helpdesk system at work has components built on Flash and I simply could not use it on the iPad. On the Android platform it is flawless and I get the same experience that I get on my Windows desktop system. It has been announced however, that Flash support will no longer be persued after the gelease of Icecream Sandwich (next Android version) as HTML5 will replace this.
This is not to say that the iPad is not a great device. It does alot of great things, is designed and built well. It just depends on what you want to use it for.
I have written a Hub that discusses the differences and similarities between the two platforms and a list of pros and cons.
Hope this helps!!!