I have used both and I prefer Ipad. It has an easier user interface and I feel like it gives you more options to customize to fit your personality better, though it is more expensive.
Instead of choosing between two products arbitrarily, you should start with the features that you're looking for. Then find a product that matches those features the best and is in your price range. The Kindle Fire and iPad are completely different devices that will suit very different purposes. Once you know what you want to do with the device, you might also find that a completely different product fits your needs better.
I went back and forth quite a bit. Several of my friends have Kindles, and several have ipads, so I got to use both pretty extensively before buying one. Ultimately, I chose the ipad for a variety of reasons. For one, the integration/ecosystem between the iphone/ipad/MacOS is really tight, and since I already use the other two, it made a lot of sense to have the flexibility and shared resources between the devices. If you're more of a Windows or Android person, obviously this won't matter to you. For another... Apple really does have the user interface experience down better than anybody else. There may be more flexibility with Android devices, more/faster hardware options, and plenty of other compelling reasons why the Kindle Fire is a better choice for some people... but for me, personally, the ipad has been a much better choice.
