What distinction can be made between devastating & incredible [see details]?

Regarding the Fujita scale used to rate the strength/intensity of tornadoes.
With the by now blanket coverage across the news channels (yeah, even over here) I saw this scale & was slightly puzzled at the wording.
The damage rating is listed as follows…
F1 Moderate
F2 Considerable
F3 Severe
F4 Devastating
F5 Incredible
I realise of course that these words are just a guide & are open to interpretation, but with tongue firmly in cheek, is there really any finite difference betwixed 4 & 5?