I am not taking sides here - just to make that clear.
Both have a point - Rams will be more confident when they are in with others of the same species and keeping 2 of them in your tank will not be a problem as they are not aggressive at all.
On the other hand, Kribensis will do fine on their own in a tank. I have a male krib in a community tank and he is perfectly happy, however, when the female was in with him at the same time, they paired up and attacked the other fish in the tank. I know as well that this happens frequently and many people end up losing fish due to stress as a result of aggressive kribs, hence the reason that people when breeding kribs tend to keep them in a species tank.
Sometimes experience speaks louder than the reading of textbooks.