If you broadcast a message across multiple platforms like Facebook, Twitter etc, and usually its an identical message across multiple platforms, you are like most people.
You are also like a pre-WWII radio station broadcasting only audio programming on television, without taking advantage of the television platform with its ability to broadcast visuals.
Time saver for sure, but bad for generating results. In a world with choices, people are more likely to respond to messages customized for them. The tone, character and emotion has to be right.
Use Twitter for short messages, preferably in real time. Though you can type upto 140 characters on Twitter, shorter tweets achieve higher engagement rates. If you have an event coming up, tweet about it. Post more tweets in the run-up to the event, and during the event. Use pictures generously. Use Facebook to create visual posts with a link. Create Ads, target posts to specific audiences. Use LinkedIn for messages that are for a business audience.