For building clients and really reaching people, Facebook is much better.
The nature of Twitter's content does not attract the same level of engagement as FB. Spending money on Twitter advertising is a waste, throw it at Facebook instead, the ROI will be far better. I say this from being in this industry and also a sports body that was spending some £10k p/m on social media advertising.
LinkedIn has good uses though. When our corporate team is pitching for contracts and business for IT services outside of our hosting brands, LinkedIn is very important not only for making the right connections but in terms of building a business profile and seeing who is working for that business.