Default to shorthand
This blog is testiment to the fact that I use contractions with reckless abandon.
I like to think it also shows a healthy respect for concision.
People use shorthand all the time when they're talking, so why wouldn't you use it in your writing?
It doesn't make any sense to me that we should make sentences longer (or less readable) for the sake of 'spelling it out' for the few who prefer it that way.
Defaulting to shorthand is a great way to keep things simple. Keeping things simple is a great way to keep things clear.