I can't stress enough the truth in what he says about ongoing maintenance costs being higher when launching a site with separate codebases for different screen

I can't stress enough the truth in what he says about ongoing maintenance costs being higher when launching a site with separate codebases for different screen sizes. This is really what sells responsive sites in my opinion: Focus. Have two versions of your site? When you integrate a new feature you have two sets of problems. Two sets of tests. Two sets of, well... everything. This is almost doubly so when it comes to content strategy. With two versions of a site it's often been my experience that one or the other (usually mobile, but I expect that to change) starts to count as little more than an afterthought and tends to degrade over time. A single responsive codebase really forces a lot of tough content questions to be asked and allows a simpler path for those problems to be solved. This isn't to say that you shouldn't do what's best for the project. A somewhat hybrid example is what NPR has done with their native / web app ecosystem. Their content is often being pulled from a single data store and brought into different presentation layers (native mobile apps on devices, HTML on the web) as needed.