Ok, porn first came to mind after re-reading it. Ive done emulating on Windows for N64 or some really old games.. Anyway..I just don't get the emulation part, Cedega or Wine ? And there are another 100 versions of Linux's ? Suse, Gentoo and "100 others" like you mentioned, well, are they just for style or do they have some actual purpose on like, lets say better performance...?
Oh, and I dont mind dual booting...unless Linux takes about 500gb of my space...
Wine, Cedega, Vmware, Virtualbox...are all different forms of "emulation". Don't worry about them, they are not essential to Linux.
However, about the different versions (Use distros, short for distributions, sounds much cooler), yes you have 100's of versions. But essentially you have 4 or 5 main ones, and the rest are just different variants of the main 5. You have basically Red Hat, Debian, Suse, and Gentoo. There some major differences between all these, especially when it comes to how you install programs.
Lets take Debian for example, Ubuntu is a Debian "child". When you install Debian you get a base system, perhaps nothing more than a command line and some essential programs, then you can add other stuff on it. You can add from 5 or 6 user interfaces (after all an interface is just a "plugin" over a base system), add your own browser, word processor..etc. However in Ubuntu you get a whole package with everything you need. The interface, the browser...etc. So Ubuntu is essentially a Debian built up in a specific set of apps to get it, the same goes for other different Debian variants (Kubuntu, Xubuntu, Mint...etc). Each built with different preferences in mind.
Ubuntu is more streamlined and user friendly because of this....I hope this explains to you "some" of the reasons of different distros.
Of course different preferences result in different performance. Gentoo is fast and stable because the "preference" of installing from source, on the expense of being hard and very not user friendly. With Ubuntu everything more or less "just works" but at the expense of having everything preconfigured to appeal to the masses.
Yes you could install linux on less than 50 Mb if you wanted to, but with Ubuntu, 10G's is more than enough as a starting point.