[absolutecleaning]

I use the 5" as well and havent had any problems, so far, with getting into corners of cushions etc

[Joe H]

If you can only afford one now - its got to be the 5". If you get the round edges on a chair arm for example, you can put your finger across part of the slot.
Get the 3" when you can afford.
Takes seconds to change over from one to the other.