As white I find the Barcza opening really easy to play. You can play the first four moves (nf3, g3, bg2, 0-0) without really needing to look up at what your opponent's doing. The moves are efficient, effective against any response as black, get your king safe, and you can start to develop without any real concerns. I play it a lot at my local club because I like to keep it (real) simple. I'm not sure where it ends and the King's Indian Attack starts but I'm sure someone will point it out.
As black I like the French because I know the general goal is to keep your centre pawns and get rid of white's and so I just play everything around that. Again it's the simplicity of the overall objective that I like.
I haven't tried the Sicilian because all the fancy sounding variations frighten me. Accelerating dragons, mincing tigers, and the budapest daschund spandex variation, it's all a bit much for me.