Two things, Food Porn that will make you drool all over and the character who knows his craft.
One was focus on a myriad of cuisine and a lot of specialty , while the other one only specializes in one area of specialty and it's noodles.
Looking for another anime like Shokugeki no Souma? Then you should watch Yume iro Patissiere. i highly recomend this anime if you like Shokugeki no Souma. They are very similar with cooking and very romantic. It is a must watch.
Both shows are upbeat with overly dramatic characters with quick mood swings.
Both main characters are excellent cooks and both shows have plenty of sake and fancy dishes.
While xxxHolic is about life lessons with a side focus of food and culture, Food Wars is all about cooking; from ingredient sourcing to history behind the dishes.
Another great thing about Food Wars is that the fan Wiki has a recipe book written by chefs who watched the show and recreated the dishes for others to try making for themselves.