The desktop will be faster simply because it is a desktop.
There are many factors that will cause the laptop to be considerably slower. And it will get slower as you load more apps onto it.
This is a false statement. A desktop will not be faster simply because it is a desktop. It comes down to the parts. Most desktops will have a faster hdd. In this case it has more ram as well. But toss a SSD drive into a laptop and you shall see.
Also a laptop or any system for that matter does not get slower as install more apps. I'm assuming you ment install apps and not loading up mulitple apps. Either way it is simply not true.