I think Twitter is great for 1-way news items and Facebook is for interacting with people. As others mentioned in this thread, most Twitter followers are people active in the same industry, which are only interested in the follow-back and really don't care about your tweets. On Facebook you're dealing with real people and potential customers. Although the real profits from social media are hard to measure, Google likes social active sites, so I think it's worth the work in the end.
"Depend on the rabbit's foot if you like, but remember it didn't work for the rabbit." R.E. Shay