Bill-O is a humorless prick, apparently catering to folks who like humorless pricks. I don't get it, I never did. I have seen him several times on shows other than his own though, and while still a humorless prick, does come off a bit more thoughtful and less partisan than one might expect.
Olbermann seems a guy who could write his own ticket in any of several venues. He has a solid resume with ESPN, or could front his own show alongside Stewart and Colbert. He's funny, quick, and wicked smart (easily the smartest of that genre, IMO). It's hard to be sure if the degree of his partisan hackery is an act (a Bill-O parody) or genuine, but I suspect he's overplaying his hand on that score for entertainment effect. Honestly, before the election, he was so far left, he was just lying down flat.
Bill-O is only interested in what is good for Bill-O, commercially and .....well, commercially. He has a market, gets big numbers and plays the market, all the time. I just watched his show, well, the last 10 minutes, most of which was reading hand picked fan and "hate" mail, commenting (how big of him to read "hate" mail then bash the author while he isn't there to defend himself), and pitching a book or some other trinket from his array of Bill-O merchandise. The first part of his show is pandering to a readily manipulated audience and the second part is merchandising. I don't watch Olbermann much at all, but I don't recall him being quite so manipulative for cold cash.