It depends. I started with microcontrollers a couple years ago and most of my projects are simple enough to be done with them. I wanted to go a bit further and remotely control stuff over the internet, the Raspberry Pi has been perfect for that. I realized that I never used the screen/keyboard/mouse and always did my development over ssh. Later, I heard about the Edison and decided to give it a shot. I'm perfectly happy with my purchase.
If I were you though, maybe I would try the Raspberry Pi first (if you prefer simplicity). You will find a lot of documentation, tutorials and projects for it. Almost everything has already been done on that platform. The price is really good too.
The Edison is a recent product and most of the projects you will want to do on it will probably need a bit more work to get going. I feel I learn more on the Edison because I have to really know what I'm doing to get stuff to work instead of just following steps of some tutorials.