Fingerstyle probably lends itself to solo guitar instrumental arrangements more. But Dan Crary and others like him can sure keep all voices going playing solo with a flatpick, too.
Playing backup to a singer sounds good both ways and it depends on the kind of sound you want. Strumming full or partial chords and doing some fills with a pick has a whole different sound than intricate sounding fingerpicking. Imagine "The Boxer" by Paul Simon if he strummed it? It'd be a different thing. And some people do it that way and it's okay, too.
Speed can be had with both a pick and fingers.
BTW, no flamingos are used or hurt in the playing of the Spanish style of flamenco.
