Gochi has better quality meat. Depending on what you get, it can be cheaper or more expensive. The dinner specials are smaller than GK. You smell a bit afterwards, and it is smaller. It uses charcoal in the grill.
Gyu-Kaku is more of a chain. They have great happy hour specials. The kobe beef items are more expensive that Gochi's premium beef specials. Their dinner specials are bigger than Gochi's. At least in the one at Topanga, you will not smell at all after coming out of there. It's more a stove with no charcoals in there.