1 - you plan to watch a season of Smallville on the iPad, as opposed to on a computer or TV?
2 - can you sync throughout the month? If so, do you need every episode loaded?
3 - a 64gb iPad can hold four seasons of Smallville and nothing else, or two seasons of Smallville, two seasons of some other show, and nothing else, or various other combinations you can think of. That is: if the goal is to be a packrat, none of the iPad options will really scratch that itch fr video.
64gb will be easier for certain needs. I don't mean to be a broken record, but my main point in this thread is that you're not deciding between "not enough space" and "plenty of space." You are deciding between 16, 32 and 64 gb.
If there was a 256gb version, we'd have a different conversation ...