One more click
With the Mac a mouse click in a window selects the window but not the focus. So as has happened to me several times already, I try to click in a text field or box and then start typing. However, my text goes into the previous window that had been selected. You have to click a second time to get the focus in the text box or field. This also applies to clicking links in a browser.
In Windows the mouse click will select both the window and put the focus where you clicked. I think this is one click more efficient and don’t see a use for the keeping the focus in the previous window. So one point to Windows XP.
Although it’s annoying when I “did the wrong” thing after only a single mouse click, it didn’t take long before I adjusted and was clicking the right number of times.