Well I am a user of both of the social networks. I find twitter a lot better when it comes to fast communication and instant updates as compare to Facebook. Twitter Trends are its most popular weapon . Facebook has trends but since its an social network made for friends, family and acquaintances so people hardly notice those trends. Facebook Chat is powerful than Twitter' Direct Message as it can support stickers, similies, Voice chat etc. and has a dedicated messenger app on iOS, Android and WP8.1. Facebook has more privacy options as compare to twitter as on Facebook you can share selectively so right people gets the right update
If you are looking for Social blogging go for Twitter (personally for me it is better than FB)
For friends etc. Facebook is better(not best as G+ is better than it)