Both have the same food based theme, but Shokugeki no Souma was more like the main character competing to be on top, while Dagashi Kashi was more like the main character trying to keep the other main character from pursuing his desire to be a mangaka. Also, both have an almost documentary like of presentation, which we the audience would learn from it.
Both have the same plot were the main theme is all about food competition, and the main characters have what it takes to make it on top. The difference however was Yakitate Japan is more on pastries...more like pattern after the great Bake Off while Shokugeki No Souma was pattern after Master Chef. Still both have the same level of exaggeration, where both shows the judge having an orgasmic experience after eating the main character's preparation.