The best for me is that you have not to trust anyone, that you can transfer funds worldwide and that you can join the system without registering anywhere. If you want more opinions, just tell me.
Many people say that bitcoin is the best because of the possibilities that it gives to a regular citizen of even badly developed country, but I think that BTC is far more than that.
You can literally pay everyone in the world for anything, just by sitting your home and with staying anonymous: all that while avoiding using bank transfer system, what is simply great.
The money cannot be tracked, the espionage agencies are not going to know what happened with your money, and where did you send them. Goverment simply cannot control bitcoin and it is decentralized: that is the thing that I like in bitcoin the most.