View source for Special:Badtitle/NS90:Talk:KWin/Default Options/2.5. Change shortcut keys for present windows - discussion: global shortcut for only one default mode

"Show windows from all desktops" and "desktop grid" are very similar. Therefore a preconfigured global shortcut for only one of this actions should be choosen. I would vote for show grid [...]"

If kwin would only predefined one "present windows" mode as default it should be the "Toggle Present Windows (All desktops)" mode (now Ctrl+F10). The focus of both modes are totally different. Desktop Grid is for arranging all open applications to the different desktops, to expand/close virtual desktops or to switch between them. Toggle Present Windows is more for selecting a window to get it to the foreground and work with this application. For this task Toggle Present Windows provide more features (name of the window, keyboard inputs to filter the window you want to work with, toogle between the windows with the arrow keys, close unneeded windows). So Toogle Present Windows is something like the taskbar but much faster in selecting windows. All the best you have not to leave your hands from the keyboard.
Since some distributions only provide one virtual desktop as default (or some people don't make extend practice of virtual desktops) Desktop Grid is in my oppinion the wrong choice for a default (if it's the only one).