Constraining what you can do with the layout? I'm not sure that makes
any sense, there's nothing you can't do with controls that you can do
with <%= %>.
Obviously the advantages to controls are numerous - they can be viewed
in template editing software (such as visual studio) because a
<mvc:literal> is a visible control. It'll even tell you the name of
the member it should be displaying, and display it in the correct CSS
style. Try that with <%= %>