Well, from what I understand, Reason includes a fair share of instruments, but only support other formats through ReWire, which for me is absolutely unacceptable. Such availibility will limit the color of your tunes, and your creativity. Plus, I've read the sequencer is terribly difficult
I use FL Studio, and although the provided instruments aren't spectacular (with the exception of 3xOsc and the boobass, when necessary), it can handle all sorts of instruments, file formats, and audio files, plus it can be used to sequence hardware.
GoodLuck
Chris