Grass will change the flavor, corn will change the flavor... If you like your friend's flavor, and it's that important, I'd copy their feeding regime. I personally like the flavor from chickens that are fed a lot of corn (I know it's not that healthy). Mine get that for scratch in the evening right now. First, b/c it's supposed to be a warm grain and I like them to have it before bed time. Second, because I like the flavor of the yolks when they're on corn. Of course, I like the variety too. Can't wait 'til Spring and fresh grass and bugs.