Off course, you can have more influence on efficiency writing servlets. But when you enter a web application project which requires (or ever will require) several disciplines, writing servlets for HTML is not the way to go. A (HTML/Javascript) web designer will probably have no idea what to do.
Furthermore, when you are writing complex HTML (with javascript, stylesheets, events and using DHTML) a JSP will give you a much better view on the output of you application.
For understanding JSP pages you need to know:
- directives
- declarations
- expressions
- scriplets
And the objects:
- request
- session
- application
There is more, but this will take you a lot further.....
Hope it helps