The more dynamic the site develops into, I think it's better to use something like GWT (or pyjams)
You don't have to sacrifice SEO by building complete site in GWT but only parts of it. That way, you can utilize best of both worlds. If you are using gwt you utilize many other grate libraries available (like ext-js wrapper for gwt) May be this is not what you want. but an attempt to use gwt (or pyjams) helps to write code in same language as we develop and is more manageable ( for me at least)
