There are 3 options: 1) Two sites, "mobile" and "desktop", both responsive; 2) One site, responsive; 3) Desktop site and mobile site.

Option 1 is the best and most expensive to implement, 3 is worst and almost same expensive. So "optimal" is 2, when best is 1.

Thanks for sharing this. Totally agree with:

"To sum it up, it is cheaper and more modern, and many times better performance-wise, to build sites that are responsive."

Yup. A lot of businesses today will try to avoid going responsive thinking that they are not a technology company. Many media companies will bring up that excuse. But the reality is that it's far cheaper and strategically better.

How is this still a question? Responsive. Next question.

or a blank page.