As far as I know, there's only one version of a mixtape. They are made to showcase talent (or lack thereof) without having to buy or make your own beats. They are a free and easy way to get your name out there. Not everybody makes beats or even has the desire to do so, and a lot of cats can't afford to buy beats. Some people have other shit to worry about before they drop money on a beat, especially when they can get down for free.
Personally I don't give a shit what beat they use. Soundclick, industry, self-produced.. It makes no difference. I listen for rhymes over everything else unless they can't spit at all, then the rhymes don't even matter. If I'm gonna go out and purchase an album, then yes, I want original beats. But when it comes to just peeping whether someone is any good or not, it makes no difference to me.