For the start, I'd like to say something to all the people who base their opinion on 30 and 60 FPS by the YouTube comparisons - those videos get it wrong. And here's a simple answer why - it's because YouTube can't display anything more than 30 FPS.
For a reliable comparison between 30 FPS and 60 FPS, it's wise to look up some of the materials courtesy of Eurogamer - a very professional site where you can learn many interesting facts you might have never known before. Here's a good one for a topic:
Metal Gear Solid V: The Phantom Pain trailer in 30 FPS:
Metal Gear Solid V: The Phantom Pain trailer in 60 FPS (simulation - it's a little not accurate, but it might give you an idea):
Personally, I'm all for the 60 FPS. It's been a standard on PCs since a long time now, and It's quite a shame that the developers still force their games to run at 30 FPS, just for additional graphic enhancements. 60 FPS looks simply smooth for the eyes.