If you have a specific use in mind, choose carefully. Capabilities and available apps vary. (about 75% of what I use my iPad for involves Filemaker Go, which is exclusive to iPad and iPhone) Get all the capacity you can afford. Cellular capability is a big plus but is not for everyone. If you're just using it for browsing, ebooks, email, music, movies and maybe some games, just pick the shiniest toy on the shelf. It will be obsolete in six months anyway.
If you are considering iPad, strongly consider the mini. Much better value than the iPad4 and it charges faster.