INTRODUCTION: I may be about to start a holy war, but this is actually a topic I’ve had to very recently deal with at work. For years I’ve standardized the theming of websites on jQueryUI and ThemeRoller. It was simply the thing to do. All the cool kids did it. It was kinda easy and if you followed the rules you’d (pretty much) avoid trouble. ThemeRoller is easy to use, there’s tons of great pre-built themes, and it got the job one. Then came Bootstrap, and it set the web on its ear. Bootstrap is more than just a theming mechanism, it’s a complete way of designing your website from both a layout and a stylistic perspective.
For years we were told the web would magically make it easy to write consistent applications that would work anytime, anywhere. For years we fought with browser incompatibilities, indecisiveness on visual standards, and a general lack of any kind of standardization on how the UI of a web application should act. Twitter decided enough is enough and dropped a big bomb on the whole net. If you want a consistent UI experience, you need a consistent tool and the appropriate conventions to go with it.
Bootstrap is that tool. Bootstrap enforces those conventions. Bootstrap not only assigns the pretty colors, but it tells your layout where to go, how wide to be based on the device, and whether or not certain elements should even be visible based on the device. All without the web developer (notice I did not say graphic/web designer) having to lift a finger. Bootstrap really is the closest thing to a magic bullet that the web has seen since ASP.Net was born.
CONCLUSION: So what do you do about all your old websites? If they ain’t broke…. But if you do have to refactor the UI for whatever reason, you should really look at converting them to Bootstrap. The shelf life of jQueryUI is basically up. Time to learn Bootstrap.