Service records on any?
what a bike looks like can be second to condition and care it has, I see plenty of "perfect" bikes destroyed by over washing so ask for records of what has been done to keep them running well.
On the carbys I would inspect
frame for cracks
studs for chrome
swingarm for cracks on the aluminum version and wether it is a early or late model.
Do they both run and run well?
which one has 10 year old tires that are now plastic?
rubber brake lines on either, should get changed.
Belts done what year?
The tube bars would be a big minus for me but I am not buying the bike.
The solo seat would be a plus if I wanted a solo bike
The better CR forks (showa) is a plus.
nice slip ons on the 900 non-cr/sp
Sticker bike looks good enough I might not change it.
CR looks close to oem outside of the tree change/mods
to have a a multi model price differentiation in the ss model range they put the 900ss engine/carbs/exhaust (americans just love the big engines) into the 750ss chassis with half fairing and that is exactly what the 900ss/cr is.
Just to clarify in the US the 750ss carby had the same aluminum swingarm as the 900 so really the forks,rear wheel width and engines were the chassis differences in the US. For us the steel swingarm started with the 900cr and was carried over to the 750ie in 1999.
Nothing wrong with the 900ie at all but which will you be happiest paying too much money for and putting in your kitchen when the wife is not home?
For me it would likely be decided by condition after a good close look/listen to them all. If all three have good frames,studs and swingarms then it is down to body style and service history. A bike that is stored with old contaminated oil is in much greater danger of having a bearing failure so who took care of the bikes? From poor pictures of one angle I would lean towards the mono but thats me, if the CR has been better cared for than that could change but I do not like a supersport/monster I would rather have a supersport AND a classic monster than the worst of both worlds.