The best? Buzz is!
I think Reason (for example) doesn't even come close to Buzz. Then what's Buzz?
A all-in-one program like Reason, but with far more possibilities. It has over 400 machines (devided into generators and effects) in many different categories. You'll find over 40 softsynths, 8 or 9 different 'trackers', a bunch of drummachines, bass machines, vst-support, direct-x-support, midi-support, soundfonts-support and loads of effect: reverbs, delays, chorus, flangers, phasers, +40 types of distortion, equalizers, +50 filters, modulation, surround-effects and a lot more...
Since it has a modular way of tracking you can link almost any machine to another (1 generator with ## of effects), wich means you've got endless possibilities.
Any parameter of any generator or effect can be tweaked on-the-fly (that's f*cking awesome!). Since it has a very large archive of machines (and it growes by the day) the use of sample becomes almost needless...
But there's one problem about Buzz: Since it is beta (and most of the machines are too) it has some bugs, wich result in crashes or hang sometimes. When you're like me and don't save your work very often, that can be a real pain in the ***: worked 3 hours any a couple of patterns and then...[ freeze ] it hangs...and everything is lost...so make sure to save your more often.
BTW...Buzz is totally free and so are the machines, updates and other stuff related. The interface in Buzz isn't very great, but that's not the main point, right? Alltogether...I think Buzz is nr.1...you can download it at:
http://www.buzzmachines.com