in the chaos version, there are some notable differences. For example, enemys hit much harder and attack faster. You also run faster. Some weapons have different modes to them and you are able to get some weapons sooner than you'd otherwise be able to. Some maps are also layed out differently. One that comes to mind is stage 7 where you have to get the crystals. Those levels are actually much easier in chaos version. The other nice thing is that your weapons cannot hit carla when she is fighting with you. One of the other intresting things i've noticed, and i'm not sure whether or not this is a bug, but normally if you take too much damage from magic bariers in the normal version your sky racer will crash. What i've found in this version is that you can actually plow through them and take endless amounts of damage. Even though you hear the crashing sound, your health will reach the negatives but you will never lose the stage.