I think generally speaking if you have enough time and money, you would make a dedicated mobile version of the site, that way you perfectly tailor the user experience for your mobile visitors.
The fact is that with responsive design, the main ‘functions’ of the desktop site cannot be changed. Responsive design is a ‘cosmetic thing’. Its the ability to control how the presentation of a page renders. It will not change how it actually works or operates.
If you have a fairly standard website that simply displays text, images and other media and hasn’t got any complex functions or mechanics then generally you would go down the responsive route if you could. The cost of production and on-going maintenance is less for responsive (you only have one website to look after). If you go down the dedicated mobile site route then you effectively have two websites to pay for on an ongoing basis.
A benefit of responsive design is that you’ll have one website that works on a wide variety of screen sizes (not just desktop and mobile but also all other devices including 7″ and 10″ tablets). The responsive aim is to get to a point where it doesn’t matter how people are looking at your content. It will restructure and flow to fit.
It’s true that page weight on dedicated mobile sites can be less and therefore loading times quicker. We have a client that will see mobile traffic become larger than their desktop traffic this year. The demographic of their users are young and they’re on the move with smartphones. They want to use their phone to buy a ticket for an event in the most straight forward, fastest, easiest way. The solution here had to be a dedicated mobile site – it simply needed to operate differently to the desktop site and needed to be lean and fast.
You could argue that pipes are getting bigger all the time so this is becoming less of an issue (and will continue to become less of an issue in the future).
Managing two websites
Also keep in mind that you will need to review content on both sites. Make sure that your content on both sites is always current and in-sync. Any new modules or features will need to be done twice, take twice as long and will need to be paid for twice.
Every website is different, just like every client is different. As mentioned previously we need to consider what your users will require from your website when they’re away from their desks. Only then can we make these major decisions about how we approach delivering your mobile experience.