the changes and advantages for what exactly are you asking?
All the changes in anything to do with responsive.css is was very hacky we merged everything the best we could into a single file and then did the best we could to simplify the file to responsive norms and best practices. We did this to eventually refactor and overall the theme for true responsiveness whihc means starting over but correctly, but did not make it that far before release. This got pushed to 3.3.
Prosilver is not a responsive theme!
The term responsive means that the entire theme was conceived to work on multiple devices which as we know is not the case with prosilver as it was not originally designed for multiple devices. It is a fluid theme with adaptive features.
Therefore using our wayback time machine we can see that they hacked together some shitty code to make it adaptive as its very difficult to make something responsive after the fact especially when you do not know what your doing which given the timeline makes sense that they did not as it was during the time when this was all new and the industry was still attempting to establishing best practices.
With this all said if you notice anything wrong or in error or just have an idea of how to handle it better pls submit it as a bug on the tracker under styles https://tracker.phpbb.com/issues/?filter=12393
and I will address it