This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
One is an HTML comment, the other is a JSP comment.
The former is just template text and ignored by the JSP engine just like any other template text and will be sent to the client verbatim. The latter is not considered template text and won't be sent to the client.