XV410
As for which is the best, the F4 got me to FL540 and M1.1 at 500' over the North Sea on my back seat trips.
I've had 1.3M at 250ft in an F3 and that was with 2x SKF and 2x 9L fitted - she wanted to go faster, but we didn't!
Soddim
The F111 over the North Sea was a difficult problem - the F3 was a bit better if it was a case of chasing it down.
That is one of the biggest understatements ever. The F3 was, and still is, one of the fastest jets at low level. It does exactly what was asked for in being able to chase down Fencers, BlackJacks and BackFires in the Iceland-Faroes Gap. I saw many a surprised "pig" and "BOne" driver learning that charging about at 700kts+ on the deck would not save them whilst on Red Flag, etc...
All said though, the F4 was, is, better than F3 at medium to high level - especially the J79 engined ones. It also has that Gene Hunt thing about it "Drop your weapons! You are surrounded by armed b@st@rds!!" - memories from another time that are long lost.
LJ