We've tried jjanga and tomo, and Umiya is our favorite out of the three. They have the best tuna and Uni, which are two of our favorite dishes.
They don't have as much as Korean food as tomo, and you have to get nigiri instead of sashimi. But the quality of the dishes (baby octopus, hot appetizers, the tuna and uni mentioned above) are definitely tops in this game.
One other really amazing thing is the speed - waiters are literally flying around and we got our food super fast.
They give you 90min instead of Jjanga's 60min so that's a win too!