Facebook is your best choice. I haven't tried Pinterest yet but I doubt it'll be better than facebook. Facebook has a larger number of users
Facebook is the best site for social media lead generation. Why? For starters, more than 2.45 billion people use Facebook every month—making it the social media platform with the largest population. Facebook also offers some of the sharpest tools to collect leads on its platform.
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Another vote for Facebook. We got our best leads from this platform. Advertisement is not cheap (depends on your niche), but for us it worked just fine.
I would say LinkedIn is a good one. Bigger database too.
Facebook and Pinterest both the platforms have different sets of audience, It completely depends on what set of audience you want to target. Facebook being more vast then Pinterest I would suggest you go for Facebook advertising. All the best.
The Most Effective Lead Generation Channels:
Social Media Marketing
Landing Page and Website Optimization
Search Engine Optimization (SEO)