Tartan is right - it all depends on what you want to do.
My husband has an iPad, but we both agree it's more of a toy than a useful work tool. He originally wanted to use it for work; doing presentations, taking notes, etc. But it doesn't come anywhere near having the functionality of a laptop.
I had one of the earlier versions of a Kindle (before I cracked the screen), all you could do on it was read books. However, I believe some of the the newer generations of Kindles have internet and gaming capabilities, which would place them in the same category as iPads.
It comes down to what kind of operating system the machine is running and what you want to do. If you want to browse the internet, check Facebook, Quilting Board, and other websites, and play games, a tablet will work fine.
I use software such as Photoshop and Electric Quilt, and create presentations and spreadsheets. Software is increasingly available for use in the cloud, but I decided I wanted the functionality of a laptop.
I suggest you go down to Best Buy and do some side-by-side comparisons of Kindles, tablets, and iPads. Ask the sales associate to explain and show you in simple, non-technical terms what each one does.