C# vs. ProIV

Question

Our company has had issues getting a new core app up and running twice now and we're looking to take another stab at this.
The developer we're in talks with right now is saying that he can create a program - start to finish - in ProIV faster than we could get someone to finish the existing C# .Net 4.0 app done even though it's more than half way complete.
Does this boast sound at all plausable?  Is C# really that slow, or ProIV that fast, or is this guy full of it?
I appreciate your opinions!