Well it really depends on your application, how you plan to develop, what IDE you prefer to use, what interfaces you need etc. The Edison is a different to the Arduino. The Edison runs an entire operating system making it much alike to a computer than the Arduino. Some tasks may be easier on the Arduino, some might be easier on the Edison, and it really depends on what the goal of the project is and the expertise of the user to make it work on both boards.
The Grove kit comes with a variety of sensors. There’s not official statement that says all libraries work without the need of a workaround however in the community users have posted their workarounds so that shouldn’t be an issue.
There’s an interesting discussion about the differences of Arduino and Edison and DHT sensors here Re: sensor DHT and Arduino 1.6.6 Help please