I would agree with Valeria. I did about six months at a B2B SaaS company managing paid search and social media. LinkedIn had the best conversions compared to Twitter, Facebook, and Google Adwords. I started testing retargeting toward the end of my time there, and we had gotten promising results. If you're target audience is more senior, think VP+, then LinkedIn has the edge on targeting specific segments.
The best advice I could give is to test, test, and test more. Test the platforms, test the copy, test the creatives.