I've had to interview people for a few C# positions and this is my general advice for VB.Net developers interviewing for a C# position:
- Make sure you are clear that you have been working VB.Net. This seems obvious but is something that apparently isn't (in my experience).
- Try to give a code sample, if possible. I've seen some horrible VB.Net (and C#) written by VB programmers who didn't seem to learn much in the transition to .Net.
- Be able to write in C# during the interview, if asked. I know there aren't many real differences between the two, but I don't want to pay you to learn the new syntax.
For your specific question: I've asked that type of question before and what I wanted to hear about was how the underlying system and framework were the same. If possible, talk about garbage collection, IDisposable, finalizers, the dangers of unsafe code blocks, stack vs heap, etc. All the kind of stuff to show that you really understand the intricacies of the .Net framework. Right or wrong, the heritage of VB brings with it an expectation of a lack of understand of lower level programming and windows in general (which, ironically enough, a c++ developer would have of a c# developer... and so on).
Lastly, how you frame your experience can make a world of difference. If you position yourself as a .Net developer, rather than VB.Net or C#, the stupid, pseudo-religious, banter may not enter the conversation. This of course requires that you actually know both VB.Net and C# at the time of the interview, but that's a good policy regardless.
The truth of the matter is that if you find that the person interviewing you writes you off simply because you've previously been developing in VB.Net, it's likely not going to be a place you want to work at anyway.