I agree with Vizon. XHTML is more reliable. If you are unstructured about how you layout your markup it's bad form and leads to more time of bug fixes etc. Coding to a stricter syntax and form will increase your productivity and as you continue to develop as a programmer neater markup will help you develop your skills not to mention allowing you to come back to a piece of work and to be able to quickly recognise what you are looking at, process it etc.

XHTML is a good universal standard that means developers can interchange code without having to spend more time to process the badly written markup.

But each to their own I guess.