After a thorough review, and based on the fact that the person using the installer is not a programmer, I've ended up recommending "Advanced Installer" to the boss. Thanks to Zumwalt for exposing me to this tool.
This product is reasonably priced, appears to have perfect integration with the Windows platform, seems to be the easiest to learn and the easiest to use, and offers support at a very reasonable price - which tells me that the product is actually easy to use and is robust.
Note that if I were running the installer I'd choose NSIS with the Graphical Install Wizard product.
http://www.graphical-installer.com/joomla/index.php/purchase/prices (€49 per license)
Again, thank you all for your input.