The likely answer is to do with audience biases. A survey conducted by an email marketing provider is almost certainly going to have different results to one conducted by PPC management tool, as their audiences have different skillsets and biases, skewing the results of their sample. As such, we should take the specific ranking of different strategies in these studies with a pinch of salt.
Not all of your site visitors are ready to talk to your sales team or see a demo of your product. Someone at the beginning of the buyer's journey might be interested in an informational piece like an ebook or a guide, whereas someone who's more familiar with your company and near the bottom of the journey might be more interested in a free trial or demo.
Lead generation falls within the second stage of the inbound marketing methodology. It occurs after you've attracted an audience and are ready to convert those visitors into leads for your sales team (namely sales-qualified leads). As you can see in the diagram below, generating leads is a fundamental point in an individual's journey to becoming a delighted customer.
Building any real, successful business takes time. Nurturing your social network presence, crafting a solid email marketing campaign, diligently working on creating and producing quality content–all of these tasks require a significant amount of time and focus. You’ll expend energy, but you have to move out of your comfort zone to achieve results – particularly when it comes to building your lead generation campaign. 

Molly K. McLaughlin is a New York-based writer and editor with more than a decade of experience covering technology. She has tested and reviewed all sorts of software, mobile apps, and gadgets. Before launching her freelance business, she was an editor at PC Magazine, covering consumer electronics, followed by a stint at ConsumerSearch.com, a revie... See Full Bio
If links and looks are set, begin interacting with the page. Abandon it, adjust the window size, convert. Are error messages appearing when they’re supposed to (if, for example, you don’t input all the form’s required info)? Is your CTA button working? If you abandon the page, are you retargeted with ads? When you resize the window, does your landing page respond accordingly?
×