Either of the majors will work good in a VW store. Normally for a small shop I would lean towards R&R because of the flexibility and slightly easier user interface compared to ADP. But with the whole R&R/UCS combination - they scare me for a small store.
You owe it to yourself to look at some of the other players out there (other than Arkona). I have a personal like for Procede (
http://www.procedesoftware.com/default.asp) for smaller shops because it uses standard Microsoft products as their backbone. It is much easier to find a local person to support the system than the majors. The trade off obviously is that it does not have the robust reporting or controls that Big Two do.