The trend is toward JSF and away from Struts. Just look at the big players.
JSF integration is more natural, with fewer "oh, but a portlet can't do this specific Struts thing, so don't ever use it" warnings.
I do
alot of portal development. I like both Struts and JSF, but for portlet develoment, I wouldn't use Struts unless it was an existing application that was being migrated.
No disrespect to Struts, because I love it, JSF is the way to go within a portlet environment.
-Cameron McKenzie