A facebook page and twitter can work well together- I've set my facebook page updates to feed onto my twitter stream. You could tweet about new products, and use twitpics to add pictures to your tweets.
It does require an investment of time, but it is free
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Facebook advertising would be a better choice for small businesses as it starts with a limited budget range. Whereas twitter advertising works out for businesses with a bigger budget. Also, Facebook ads has a wider reach and is more effective than twitter as of now.
Both are the best for advertising but according to my point of view Facebook is better than twitter because in the Facebook we can create friends very easily as compare twitter and lot of facility also available in Facebook.