It all depends on your niche, but if you have 1m followers on one of this networks I am sure each and everyone will work for you, you just need the followers that's all.
Twitter followers are not click my links, even though I am in a web design niche with one of my sites, on the other hand, Pinterest is doing great when your in a women niche, eg: recipes, DIY etc.
Facebook I think it's probably the best, I mean, who on earth doesn't have a Facebook account. If you plan your marketing right you can reach 1m likes, but remember to work hard and smart at the same time.