advantages: Nothing
Disadvantage: An increase in the chance of bricking your phone and finally throw it away.
False. There are a ton of possible advantages.
However, the question is mostly, do these advantages matter to you? Some people with lower end phones root to remove huge system apps like Maps, Hangouts, Google+, etc. This allows them to free up space in the system partition, which using root access, they can install apps to. Unrooted devices can't do that. Also, rooting phone can increase their life-span. My Galaxy S and Galaxy Tab Plus have better specs than some current phone being released with ICS/JB, but due to their age have had support stopped from Samsung. However with root, I can give them JB and not spend a thing.
Higher end phones don't normally need that, but root gives them other advatages. Certain automation features now need root access, so if you use Tasker, rooting is quite important. Security programs like Cerberus, Avast, Lookout, etc, also work better with root. You can make it so that a reset of the phone won't erase them, allowing to to trace the phone even if factory reset. Custom apps also have better access when rooted. For example, exDialer can't dismiss the missed call notification if you aren't rooted. You still have to open up the stock dialer.
Then there's a whole lot of other stuff they do over at XDA.
Plus rooting nowadays is just a one click process for more popular phones. Almost absolutely zero chance of bricking if you have one of the supported phones. As I said, you should read properly. You may miss the one click installation instructions, download from the wrong link, etc.