I have both products. Comparisons of the two often don't go very well here. Both have there own merits and I see them as seperate. Both have been lovingly and respectfully created. I support both A2A and warbirdsim by purchasing their products. The A2A Stang is about the accusim, that and the model are an awesome work of art. Warbirdsim's Stangs are about the the diffrent types of Stangs and the small details are AMAZING! The amount of detail and paints available for Warbirdsim's Stangs make it well worth the money.
Both take attention to detail to fly successfully. I would have to say that it's about personal taste, and what you are looking for. I'm happy to have both in my hanger!