How big is "big"? Big is a relative term ;)
What are your matrix points in this consideration? Network? Bandwidth?Security?User experience?
One point to note though. If your users are in a tightly controlled environment, where they do not have admin. rights to install stuff on their workstations, JWS might be a problem in cases like java version mismatch.
I think developing rich, complex user interfaces that involve for example graphics, charts, lists, tables, frequent entering data, is a lot easier when using frameworks like Swing (or Flex for that matter) then any web framework.
My guess is an experienced Swing, SWT, Flex, or Silverlight developer can develop any user interface a lot faster then an experienced jsf, struts, html/jsp developer. Also, end-users will usually be more productive as they have wait for user updates less longer, can use keyboard short cuts better.