I have nothing against imitation crab (sometimes called krab or surimi) but sushi made with real crab just plain tastes better. It just plain costs more, too. I recently read a story about the nutritional difference between the two, and crab clearly trumps krab.
Both crab and krab are low in fat, therefore neither is a good source of the prized Omega-3 fatty acids found in other seafood, but real crab has more protein, more potassium, and less sodium than imitation crab. That’s all fine and good, but for me, taste trumps nutrition and that’s why I’ll pick crab over krab any day of the week.