I used Fruity Loops 4 until the day I discovered Reason. I'll admit I was no expert with Fruity Loops, but I was mildly competent. But Reason is, at least in my experience, far more versatile.
Rewire is an interface whereby you can "connect" multitrack software to a program such as Reason or Fruity Loops. For example, I use Sonar 5 and Reason together. When I insert Reason as a Rewire device into a Sonar project, Reason opens up and is now controlled by Sonar. They work in tandem. If I press play in Sonar, it plays in Reason and vice versa. All MIDI routing is then done through Sonar to Reason (which can be a pain sometimes, but oh well). It's very handy because it lets you do all of your recorded audio in one program and hear all of your synth work simultaneously.
