I would go with the Koral. The Vulkan Gi's are very light which is a good thing for competition. But I find that the heavier your gi is, the more it helps you become a better grappler.Not only is a thicker gi more durable, but it is heavier which makes you work harder and in turn you get stronger,(kind of like running vs running with light weights on your hands and feet). This effect is magnified even more when you consider the thicker gi holds more sweat, which makes it even heavier and makes you get an even better workout.
Not only does it increase strength slightly, it also forces you to become more technically sound with your BJJ as a thicker gi is easier for your opponent to grab and hold on to. This forces you to work a little bit harder to maintain position and in turn, your BJJ game will become better as a result of this.
Go with the Koral, it will last longer and your game will improve as a result of this!