What are the differences between C#.net and Visual Basic.net?
Performance is equivalent if you write equivalent code, but VB.NET has constructs that are in there for "backward compatibility" which should NEVER be used. C# doesn't have some of these things. I'm thinking specifically of:
Functions which are in the Microsoft.VisualBasic namespace which are members of other standard .NET classes like Trim(). The .NET classes are often faster.
Redim and Redim Preserve. Never to be used in .NET, but there they are in VB.
On Error ... instead of exceptions. Yuck!
Late binding (sometimes derisively called "Option Slow"). Not a good idea in a non-dynamic .NET language from a performance perspective.
VB is also missing things like automatic properties which makes it pretty undesirable for me. Not a performance issue, but worth keeping in mind.
The Language Features section of the Wikipedia article offers a good overview. Performance is essentially equivalent in almost every aspect, from what I understand.