Facebook is quick and to the point, with instant gratification. I can get off quick.
Livejournal requires more... attention. But with a little effort, it works for you and facilitates everything you ever want. Facebook just gives you what most people want, which satisfies the here and right now, but if you have anything thats out of norm, then you just don't get it. It's shallow.
That said, I look back on what all I've posted to LiveJournal in the last several years and... I'm amazed. I haven't changed a bit in 4 years.
Not entirely true... I've progressed materially. I have a house... but mentally, I've digressed. I don't work projects that are as meaningful anymore; I don't think thoughts that are as controversial anymore. I don't engage people in mentally challenging conversations anymore so much as I just flat out tell them they're stupid.
I blame Facebook and it's short character limit.
I'm back on LiveJournal, I'm engaging my brain again, and I'm looking for new projects to learn and explore with.