Not really a lot. The carbon limbs are tougher and more consistent. They are also lighter, but not much. They are impervious to extreme temp. changes. If you store your bow inside, where it's warm, and go outside where it's 20* to shoot.....it will take the limbs a little while to acclimate to the temps, and your accuracy will suffer, all be it not much. In about 15 minutes, it's all good. You'll get a little more speed w/ the carbon limb, little better KE. They're a little quieter, less vibration and recoil. They are just an overall better limb.

BUT, not a whole lot. Are they worth the money? Well, that's up to the individual.