Hi, (don't turn this in a flame)
Thats almost impossible. KDE vs GNOME is highly subjective, and completley dependant on what you want. I love KDE and loathe GNOME, but some people see it the other way around.
Luckily for you, there both free, and come with most distros. My advice is to try them both out, and use them for a week each. In the end you will have a solid idea of which you like best.
Then every 12 Months or so try the one you didn't choose again, just to see if your missing something good. Also don't forget that GNOME programs work in KDE, and vica-versa. So your not stuck with one more than the other. ( although the programs will look better in the enviroment they where desgined for. )
AS for the pros and cons, I won't even go there