Harry - 2:33 pm on May 8, 2012 (gmt 0)
@rlange that's part of the problem with responsive design although as mentioned by @incrediBILL there are ways to serve images to mobile devices but they do involve a lot of compromise in themselves and are still not exactly full-proof and easy on the user's device.
Responsive design is cool and like I wrote above, I use it too. However, it's a stop gap solution at best and will not perform as smoothly under all scenarios and devices as well as a dedicated solution for mobile.
What responsive design handles well, is the middle ground occupied by tablets by being well adjusted for viewing contents on them. But there's always a loser in a one size fits all solution and in this case, it's rarely the full desktop which usually has more power, a better connection and better resources to handle anything and not really lag. Mobile devices, by their nature are finicky. You have to assume that your user is using the worst data access, that their device is slow, has a full cache will not handle particular tricks as well and so on. Just resizing images and reflowing texts and menus vertically and removing a few useless plug ins will not be enough.
The whole point of responsive designs is to serve mobile users better, but it usually means that they get the worse experience of all users. On the other hand, a dedicated mobile site does away with a lot of the crap and only delivers what a typical mobile user needs. There's no complicated media query trick to remove offending material or to resize stuff and load alternate CSS files. If it's done properly, it's built from the ground up to be as lean as possible.
On my sites, this is actually the case. The mobile site loads way faster than the responsive one and is easier to navigate. it just works. Often, I find that using the mobile site is the even easier to use with older browsers and those that don't support HTML5 or render something out of whack (looking at Chrome and IE).
But since the current in thing is responsive design, there's no point arguing that it works mostly in theory but is not the prefect solution for everything.