Its hard to say whether a Razorwing is better than a Ravager, as the Ravager has an extra Dark Lance and is cheaper. But then the Razorwing has anti infantry and horde affects s well.
But it is onyl an extra 40 points, and it comes with the missiles, splinters, and Supersonic and aerial assault. So personaly I would say it is a good move. And it is what I would do.