JSTL is an advanced programming system that offers a simpler and more consistent programming environment than JSP scriptlet code. You must consider many factors when deciding whether you will use JSTL or not. You must consider the number and skill sets of people who will be working with your JSP pages.
If your Web application is developed by a small group of advanced programmers, you may not be best served by JSTL. These programmers may prefer to simply code the JSP to do exactly what they want and have no need of JSTL.
If your Web application is a large project and has one or more graphic artists or other design people who work together with programmers, you may want to consider JSTL. JSTL allows your HTML programmers to program in one consistent environment. Your back-end programmers still create JavaBeans, which are used in conjunction with the JSTL code that will be contained in your projects JSP pages.
These two suggestions are not hard-and-fast rules. You must always evaluate your company's situation and use the correct technologies. Then, you will be able to make an informed decision about the suitability of JSTL to your project.