What space are you working in, what other equipment are you working with, and what are your overall goals? Plus, what is your budget to work with?
There are loads of pros and cons to various options, and the best choice really depends on different factors. Having access to different backgrounds gives you different options, and there is lots to be said about having black, approx mid-grey, and white on hand to give you flexibility. Grey is great if you have the lighting gear to be flexible with how much light you're putting on it to make it anything from black to white, but if you're aiming to crush the background completely then starting with black to begin with makes controlling spill far easier.
If you're not needing excessively wide, then I like working with paper back grounds from a photo supplier. (If I'm working really small stuff, like table top, then I honestly just go ahead and buy poster board from a local arts and crafts supplier rather than spending the extra cash on rolls of photographic background stuff.)
If you're backing a wider space in a larger studio, then I've found cotton fabric gave slightly fewer headaches if combined with a decent commercial grade steamer. (Getting a good black took some trial and error at a local fabric store. First few we tried ended up with an excessively awkward to work with sheen that highlighted in weird ways. Black fabric was also always a pain to keep tidy looking. Do not let anyone with glitter near black fabric in a photo studio...)
While you can overlap paper on really wide spaces, I've found it to be overly at risk of getting crinkles, and that kind of diminish their value. Fabric felt more fault-tolerant with carefully made seams, but a full black back drop was horribly annoying