I've noticed, that your installers behave differently when updating an existing installation.
I'm just using PDF XChange Viewer as viewer application for PDF documents and its installer is quite fine. If I'm updating an older installation, all settings will be remembered (selected components, installation directory, choices about creating groups and and being the default application for PDF documents).
The installer for PDF XChange Pro behaves differently. If I'm updating, while the selected components are remembered, I'll have to reset the target directory and also the settings for default PDF viewer and default printer.
Also the "Vault" is always installed to the default directory, in one of the two installers, while the other one uses the alternatively specified installation directory.
It would be nice, if the last used settings would be also remembered in PDF XChange Pro setup.