As a bit of a RF newbie (though not electronics) I opted for the GAMMA shield. Really easy to use and the coding was very simple to something up and working for testing. Of the two I bought, only one is really using the capabilities of the Arduino, the other (transmitter) is just sitting atop an Arduino for power and a heartbeat signal that could be generated from a old 555! Next time, I would be brave enough to go for the just the GAMMA module, but the GAMMA shield was a great way to learn. Used for a one off water level sensor for our private water supply about 1 km, but not line of sight - range great!