What ridifvx says is not strictly correct. C# is not more responsive in speed, and neither language is designed more readily for any particular types of application. C# is not a sucessor of C or C++ either. Check out the Microsoft White Paper, and here's a quick quote from that to get you started
‘…the key point to keep in mind is that .NET is intended to be language-independent. The choice between Visual Basic .NET and Visual C# .NET is typically based on your personal preference and past experience…’
Whatever language you use to write .Net applications in, they compile up to the Microsoft Intermediary Language, (MSIL), ready for the Just-In-Time, (JIT), comiler. There are a small number of things you can simply do in VB.net that are more complex to undertake with C# and vice versa, but generally it's a matter of preference, or knowing both, (or more, don't forget J# and managed C++), and selecting the best tool for the job when you know what you're trying to acheive.
The .Net framework is where the power is, and where you'll generally find more gains from writing applications using Visual Basic 6.0 for example. The choice of programming language with which to leverage the .Net framework is considerably more a choice of implementation, based on your given requirements and skill set.
Rhys
Be careful that the light at the end of the tunnel isn't a train coming the other way.