I've had both Poser 11 and Poser Pro 2014 installed on the same computer and never had a problem with them. Poser 11.1 is my problem. The two versions did share the same runtime folders which are on a separate partition, but that was never an issue. I've never had both Poser 11 and Poser 11 Pro on the same computer (I have both versions) so I don't know if one would uninstall the other. It probably would. Earlier versions don't seem to be a problem.

Poser 2, 3, 4, 5, 6, 7, 8, 9, 10, Pro 2014, 11, 11 Pro