I agree that Smiley Face "focuses more accurately on pothead inertia and stoner behavior" than similar movies. Araki was consciously and adamantly looking for something light and comedic following the wonderful and "heavy" Mysterious Skin when he came across this script by Dylan Haggerty, a minor actor who plays the Ferris Wheel attendant in the movie. The humor derives from close observation or intimate knowledge of the self-absorption, self-consciousness, overvigilance, and altered perceptions facilitated by the popular herb. Smiley Face doesn't "reach" for laughs; it seems grounded by experience. And Anna Faris (Cindy from the Scary Movies) is just right for the central role.

I failed to find any direct quotes from Fuller but, for what it's worth, what was said on TCM about Park Row being his favorite is echoed on Fuller's Wikipedia page. No doubt he's proud about The Big Red One; it's such a personal work.