Selected answers from the Dumb SEO Questions Facebook & G+ community.
George G.: to domain.comalso 301 redirect /index.php > domain.com
Michael Martinez: You will mosy likely get an error trying to redirect an index url. I would canonicalize to the shortest possible url.
George G.: depends on the cms. the error wont be from the index file but form the htaccess setup. assuming he asks, index is a valid url, hence - redirect.
JL Faverio: Thank you. Then I`ll rel canonical to the domain.com.