This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I think difference lies in the way they get input content instead of the return type. Servlet gets only HttpRequest/HttpResponse objects where as for REST method you have control how you will provide input to it..