Interesting point.
I tend to use my 3-9x40 at 4x, although I have used 3, 6 and 9 depending on exactly what I'm trying to do.
I decided to give up on my fixed PX scope, because usually I shoot at between 10 and 20 yards in my garden - not good for the 35 yard PX - so I ordered myself one of the JSR 3-9x40 PX IR scopes to replace it.
Does everything my old scope did better - then does a load more on top, all for a decent price.
Perfect - very eager to see it arrive.