1 expert has answered
I would consider them both to be as equally 'safe' as each other.
Facebook is designed to connect you with friends and is more 'private'... where as Twitter is intended for the public (anyone can see your Twitter posts and contact you).
Both have privacy settings (i.e. Facebook allows you to share with friends/public etc and Twitter allows you to protect your Tweets) - it's just a matter of how individuals use those settings, which affects the overall level of 'safety' for them. For example, I could have all my Facebook content open to everyone on Facebook but my Twitter posts could be protected and only accessibly by those I approve, therefore Twitter would be the safer platform (visa-versa).