1. Ease of use:
Probably the most important category.Unity has a great launcher with appropriately sized icons,it has the dash which is easy to navigate and it has the hub.Everything is a few clicks away.KDE on the other hand has pretty standard ease of use..A pretty standard taskbar similar(the one that windows 7 ripped off).Nothing special there.
2. Startup speed:
People complain that unity is slow,but KDE is even worse.
3. Customization and personalization:
Unity can be configured pretty nicely if you know how to do it...However KDE is unbeatable there.The most configurable interface right now.With enough creativity you could make it look like it was done on crack.
4. Out of the box beauty:
Out of the box both are pretty good.It is just that Unity is a bit more composed,has a better default wall paper,a better default theme and some minor pluses.
5. After customization beauty:
If you give it some effort you can really make your KDE interface shine.It has tons of effects,a multitude of great themes to choose.And you can pick colors for everything.You can move your task-bar into any side of the screen,even put it in the middle of the screen,you can change the size and shape of the task-bar both vertically and horizontally...
The desktop in unity is as neat as its user.Nothing special there.However KDE has some features which allow you to keep your desktop neater.It has this kind of "fence" where your icons,folders and documents are.You will see it on the screenshot I will provide.
Here is a screenshot of my Unity desktop.The only customisation here is the wallpaper:
And here is KDE.What you see there is how the wobbly windows effect works,once you move a window it becomes wobbly :).This one is heavily customized:
So its a tie with 3:3!