No, it's not impossible to do two socks at a time with magic loop. I've done it. But it's not as portable as it is with doing one sock as you are constantly sorting it all out! There is an AOL support group for this that has a great wealth of material on it.
IMHO, neither one is easier than the other. I learned top down first...which is what most of the tutorials I know of show. I like the toe up better though, because you can just keep knitting until you use up the ball of yarn, rather than having to hope you end up with enough left once you get to the toe.