I think there is a difference between the two!
A web application developer where I work may know very little about front end design. This is especially true if you work on a business intranet, where as long as something gets the job done - it's good to go! Web App Devs focus more on business logic and meeting minimum data requirements. If the data appears, it doesn't matter how it looks or what someone had to do to get it there. Hence, I wish where I am at now would raise the bar and allow me to focus on....
Web Developers are typically perceived to know more about front-end coding, using HTML, CSS, jQuery, Flash, and the like. I think they tend to focus more on usability, ease-of-use, efficiency, and similar things
These opinions are wrote from my experiences within a large company with a small developer team. My co-workers care less about how something looks (we are all technically web app devs), so I, the 'web developer', put the usability aspects in place and polish before we release stuff. Yeah - the management could improve this flow, but it works as it is.