The two fields are very much similar in terms of the required aptitude and knowledge. It is a fact that both of them would need deep understanding of web development and software engineering. The main element that support has that is not in development is communication. As a support, you communicate with your clients through their experience with your product and it continues on as they adapt to the system. You can affect their business directly by the knowledge you share to them. In development, you do need communication skills but it's not as essential. You can even waive it off completely by having your client fill out a some sort of request form and communication ends there. You're just going to rely next on your project manager for revisions.