Classic OS vs OS X

I know that this question has been asked before, but I never got a clear definitive answer.
Here is the question. Why did Apple decide to go for the Unix shell for OS X?
I understand that given the progress and the coming release of leopard, its kinda too late to be asking that, but I would really like to know what was wrong with the classic OS kernel???

Back when I was a kid, I used to love seeing the classic OS. I like the feature in OS 9 that you could just speak a password or phrase and it would log me in. There is no feature like that in OS X.. as far as I know. Besides... the old OS was Apple's own invention from the ground up... it was infinitely mor better than what Microsoft was giving its users.... ;D

I think that the Mac OS had run its time when it was replaced by the FreeBSD/NeXT/Unix connection. It was fragile in terms of stability, when it was running well it was ok, of course, but when extension conflicts arose, it was a pain to manage them and find the culprit. Back then, when you had a crash, the whole system was brought down along with it. You couldn't multi-task (have more than one application running tasks at the same time). Etc.

That and the fact that developers were more and more leaving the platform for either Windoze or Linux development. It got to the point where, if you didn't hear of at least one defection in the development community, it was a good week.

For technical background to your question, you might want to download this pdf file, A Technical History of Apple's Operating System by Amit Singh (it's a supplementary document for Chapter 1 of his book, Mac OS X Internals: A Systems Approach.

Thats a fair enough answer I think... ;D