CocoIchi is by far the choice among choices. For me anyway. Yoshinoya is a not distant second though. I tend to roll in after the sun is up on weekends though, and a stop at CocoIchi is a near must for me. YMMV.

But back to the original Q, beef in Japan is largely cooked in away to that hardly brings out its best characteristics. If you took a decent chunk of Japanese beef to the US and had a decent steak restaurant prepare it you would receive a better pure "meat" experience. The Japanese are more into balance, accent, presentation, and other sublime things when preparing and presenting food. I would say go to Japan for the whole meal, but stick to the US, Argentina, etc. for the pure beef experience.

That all said, I think I am reading the original post correctly when I assume that the goal of the meal sought is a carnivorous feast highlighting the flavors and textures of Japanese beef as opposed to a delicately prepared and presented Japanese meal. For that I would recommend going to a very good Shabu Shabu place and enjoying too thin to believe it is possible cuts f the very delicious Japanese beef accompanied by all that is a lovely shabu shabu meal. You can dine and dine and dine on platters of beef and really enjoy a flavorful experience that will endear you to Japanese beef forever.

Mike