There is almost nothing similar between Reason and Kontakt. It's not even like comparing apples to oranges. I'd suggest reading up a lot more on the two at their websites to see what might work best for you, and really try them out if you can. You can download the Reason demo, but I don't think Kontakt has a demo.... so read up on NI's website and watch their videos of it.
As has been stated, Reason is not a VSTi, but rather a completely stand-alone modular music creation environment, with tons of built-in synths, fx, loop players, samplers, its own sequencer, and so forth. You can consider it as an external crazy-huge-modular rack of synths or a very powerful workstation that syncs with Sonar, or you can work 100% within it, and forget about Sonar for a while. It is NOT a DAW, nor is it a HOST, so it doesn't compete with Sonar in that way, but it far more than any other plugin out there in many ways. Does it sound good? Yes, if you like that sort of thing. But I also own a lot of other plugins that sound as good or better than any individual element inside Reason. However, it is fun to use and it is very stable so you can spend a lot of time in there. I happen to like it a lot. Again, you need to test it. It works fine "rewired" to Sonar, although I prefer to use it standalone.
Kontakt, on the other hand, is a top-notch, super-powerful sampler plugin. It is quite good for what it does, and it does everything you would pretty much ever want a sampler plugin to do, and then some. Because it's so powerful, you CAN do some very synth-like things with it, and it does some really neat things that I never expected, but it is, after all, a sampler. 10 years ago, no one ever dreamed a sampler could do the things that it actually does now, but again, it is what it is. I also use it, and it is indispensable in my projects. It also comes with a HUGE library out of the box, and it is quite usable. However... again, it is a sampler.
Since I have so many synths, I could easily live without Reason. However, I think it's a great environment and it can do some very amazing things. If it fits your workflow well, you will love it. Bottom line: not many of my projects use it, but I do really think it's great.
As for Kontakt, it is so integrated into my workflow, that it would be very difficult to get rid of it now, and believe me, I have wanted to in times past. I have a love-hate relationship with Native Instruments, they have caused me a lot of grief. But at this point literally every project I do has at least one instance of Kontakt in it, so it would be very difficult for me to get rid of it. And at least right now, it is behaving pretty well, so I HAVE to use it, and slowly the pain of dealing with NI recedes in my mind. It always takes a while for things to work when new versions come out... but now Cubase, Sonar, Kontakt, etc., have settled into a nice truce on my DAW. But no doubt NI will cause me more stress in the future when the upgrade cycle begins again.
Your mileage will vary depending on your workflow and needs. Since there's so little overlap between them, you may want to get both. If you can only afford one right now, and you aren't attracted to the excellent synths inside Reason, and you already DON'T have a sampler, Kontakt might be a good start for you... Good luck!
post edited by eratu - 2008/03/03 17:39:01