I have used both JSP and Thymeleaf.

Pros of Thymeleaf:-

• ThymeLeaf is a healthy open source project: new features coming up each month, good documentation, responsive user forums
• It is the ideal template engine if you want your web designer to be able to read your view files
• The Expression Language used (actually called Standard Dialect) is much more powerful than JSP Expression Language.
• Unlike JSPs, Thymeleaf works well for Rich HTML emails (see http://www.thymeleaf.org/springmail.html).

Cons of Thymeleaf:-

• Thymeleaf does not have an equivalent to custom tags (.tagx files) yet.
• At this stage, ThymeLeaf is not compatible with JSP tag libraries.

Pros of JSP:-

• Eclipse/STS works well with custom tags so you’re able to use CTRL+space for auto-completion.

Cons of JSP:-

• It is harder to Unit Test your view layer.
• Documentation is not the best.

I use JSP/JSTL because it is a standard. In addition to that, I also use spring forms and tags in addition. Your IDE can suggest tags and attributes because it is XML based on your JSP.