I know this is an old question and must have been answered hundred times already, but I am not able to find a satisfactory response as yet.
I am creating an applicat
I guess the web application vs web service is the fact that the deployment factor ratio vary meaning the deployment of a web application would be limited (locally ) to what as in case of a web service (globally). Plus, When we think of UI perspective better option is the Web application but when we think of programming and data transfer perspective mainly go for a web service. Web application requires use of servlets with frameworks like Spring mvc etc. On the other hand, if you want to deploy the same application to multiple platforms make it a web service via Rest/Soap implementations so that the web applications behaviour gets changed to rather a service.
In short,
WebService =
(RestApi/Soap) # added
/ | \
(client1)---(Web Application)---(clientN)