I prefer the f4 200mm too. I use a early MD Rokkor (the large one) version and its sharp from wide open if I get the focus point right.

Two or three years ago I compared it against a M42 SMC Takumar 4 200mm and a Pentacon 4 200mm (yes the cream machine with the many apurture blades) and a Panagor 3.5 200mm on my digital A900 camera and would call it a draw concerning sharpness between the Rokkor and the Takumar, because the Takumar also impressed me with excellent sharpness and contrast.
The Panagor looses a very little bit in conrast, and the Pentacon is a complete different beast too, it has a complete differnt rendering and stopped down to f5.6 its sharp too but not as biting as the Rokkor or the Takumar.

My MC Rokkor 3.5 200mm is a very little bit softer wide open compared to my Rokkor f4 and larger and heavier in the bag.

I have never used the f4.5.

What can I tell? I love them all they are all very good lenses (outresolving the A900 24MP sensor in the center), and I would never mind using any of these lenses.

BG lightdreamer