The first company is not proof that social media works. That's not the issue. The issue, of course, is that social media simply "is". It's no different than the focus groups and surveys of twenty years ago. It's both marketing and customer research. It's data. It just "is". You cannot separate social media from the rest of the branding elements of the business. You can't. You cannot prove that social media works, and you cannot remove it from the business. It is not a tactic. It simply "is" the business. And customers are acquired cheaply as a result.
The second company can easily prove that social media doesn't work. They should know. They tried putting some sale messages on Twitter, and nobody responded. The second company is fully confident in their merchandising team. The second company just needs to find marketing channels to communicate the merchandising strategy to the customer. The second company is going "omnichannel". They'll ship-to-store or buy-online-pickup-in-store or get you a discount on your mobile phone when you're in the mall (if the customer ever steps foot in a mall anymore).
Retail is moving in two different directions....
Kevin Hillstrom shares a thoughtful post on whether social marketing works or not.