Posting on Twitter and Facebook differs a lot, not just because of the different maximum message lengths.
When you post on Twitter, your message is available for anyone on Twitter to read. This is an obvious advantage compared to Facebook. When I post on Facebook only my Facebook friends will read the message. If I want a lot of people to read my message I need a lot of friends. I might also have a Facebook page and try to get lots of people to like it. Whatever way you choose, it may take a long while to get enough friends. If I search on Facebook all I get is people or pages whose names include my search, when in fact I would like to find key-words in messages.
If you have something to say, Twitter is probably the better alternative. However there are more efficient ways of using Twitter. Your message is likely to benefit from including some tag, which is the #-sign immediately followed by a word. Any word will do, but it's better to use some word a lot of other people have already used. To get some tag-tips, see http://hashtags.org/. There you'll also see how often and recently they've been used.
If you're looking for a new job, you could search Twitter for #job or #freelance and many more tags. If you're looking for celebrities, you could look for #charliesheen or #ladygaga.