Of all the Microsoft developed languages that can utilize the CLR, C# (arguably) is the best balance of power and elegance. More importantly, it is what Autodesk will provide the most support for (guess) and it has the largest user base if I'm not mistaken.
If one is thinking "Ooooh, but I've x years of solid development time in VB6, I should learn VB.Net" save yourself some grief. The learning curve for VB.Net is very similar to C#. VB.Net shares little with VB other than name and some syntax, but you'll just bring your bad VB habits (yes, you have some) along for the ride to VB.Net. Notwithstanding, I think M$ had an excellent opportunity to make VB.Net an improved version of VB, but they didn't. Instead they retaining some real lousy VB paradigms for no good reason (which they had initially intended to abandon); it's not like VB6 code magically ports seemlessly to VB.Net. Anyway, it would be better IMO opinion to just buck up and learn C#.
But I digress!