Hello and welcome to JustAnswer!
I see that your question has been up for an extended time without a response and while Porsche is not my area of greatest expertise I would like to try to help.
The shape of the cars and maintenance history would be a big factor in my decision on which one of these to buy. Even though the cheapest car has the most kilometers on it, it's possible that could be the best car out of all of them. Vehicles that are driven more often outlast cars that sit and aren't driven much. For example on a car that sits it can allow the brake rotors and drums to rust up, caliper pistons to stick, excessive rust, etc.
Maintenance would be a big factor, if you could find out any history on the vehicles. If the highest km car has been well taken care of and the others didn't get as much care then it may be a better choice.
The intermediate shaft bearing problem is more likely to happen on a higher km engine or one that hasn't had proper maintenance. By time alone, the one with the highest km would be the most likely to have a bearing failure, but if it has been taken care of well and the others haven't then it may very well outlast the others.
One thing to consider is banks are less likely to loan money on a vehicle with high kilometers. It is really on a case by case basis, but a bank may be more willing to loan the money for one with less kilometers, or possibly give a better rate.
It wouldn't be a bad idea to have a trusted mechanic at least look the cars over before you make a decision. If you have someone that you could bring along to look at them or have a trusted shop that you can take them to then you would have a better idea of which car would be better for you.