1) Vista Home Premium is the best for home users, not Business, because they would make better use out of the features in Home Premium. Honestly, go look up a comparison of the flavors, it's not hard to find.
2) Vista "upgrades" migrate user settings, data, and junk to Vista but it is actually a clean install. It's more like a "wipe and reload" according to this technet article:
Windows Vista Installation
Now that you know a bit about ImageX and the WIM image format, I bet you're wondering what the disk-image deployment process looks like. Installing Windows Vista, whether doing an in-place upgrade or a complete wipe-and-load, is a new, completely image-based process.
In fact, Windows Vista ships exclusively in the WIM image format.
In fact, the in-place upgrade process works better than it did in Windows XP. The reason is that upgrading to Windows Vista is really a clean installation with the migration of user settings, documents, and applications from an older version of Windows. The in-place upgrade process is better named wipe-and-reload.
The following steps describe how you use these tools to deploy a Windows Vista disk image:
1. You can enhance a Windows Vista image by using the desktop-engineering tools that Microsoft provides for selection of device drivers and optional components such as languages.
2. You install the image on a test computer, add applications (e.g., Microsoft Office or a Line of Business Application), and then save the image to the network.
3. You deploy the image to the user by using tools that Microsoft provides. You can completely automate the installation by using the new scripting and answer file capabilities that Windows Vista provides. If you are upgrading a computer from an earlier version of Windows to Windows Vista, then the setup program will migrate users' documents, settings, and applications without prompting the user for input.
http://technet.microsoft.com/en-us/windowsvista/aa905070.aspx
