While it takes a bit more work to manage two channels, having a separate "stand alone" mobile site (next to your desktop site) can have it´s great advantages.
Opposite of a responsive site, a stand alone mobile site is served by it´s own unique HTML-code which means that it can be differentiated completely from the desktop site - both with regards to content and design.
Furthermore it has it´s own unique SEO tags which means that it can be optimized better for search engine user´s operating from mobile devices. In other words it can be built to serve mobile user´s better and convert more of them into customers than the avarage responsive version of a desktop site can.
Having a stand alone mobile site is recommendable for site owners who want their mobile site to be designed in a 100% optimized way for mobile use and who are also concious of the fact that mobile-friendly content often differ from content consumed on larger screens.
Building a stand alone mobile site is very easy. The mobile site editor works according to the exact same principles as the desktop editor with regards to page structure, design and modules. New readers should start reading the desktop manual to get a hang of how things work on the mobile channel as well.