The quick answer:
QuikClot gauze is impregnated with a substance called Kaolin, which is basically a white clay. Celox gauze is impregnated chitosan and other Celox proprietary elements.
1st gen QuikClot used to cause secondary exothermic reactions. Subsequent generations of the product no longer produce exothermic reactions; both current gen Celox and QuikClot will not cause any tissue burning.
Both products work with the bodies clotting cascade to form clots. Both products have differing methods of action, which is to long winded and technical to get into right now.
I prefer Celox because of it's ability to coagulate and clot heparinized blood, hypothermic blood and patients on a antiplatelet medication. (EDIT) With a very large percentage of the population who are on or take medications such as Coumadin, Plavix, Aspirin etc, this is a HUGE benefit of Celox. And in regards to hypothermic blood; keep in mind that our patients could, (but we hope not) are displaying some phase of hypovolemic shock which in turn will cause a decrease in body temp as they slip further down the chute. +1 Celox.
Also, are we operating in a cold environment or during the winter season? +1 Celox. Was the patient found in cold water? +1 Celox. These are just some random examples why Celox may be a more effective hemostatic compared to others. I must disclose that I do not get paid by any of these companies. I'm just kind of a nerd when it comes to this stuff.
Hemostatics in granular form are basically being phased out. Current TCCC guidelines and protocols call for hemostatic gauze. Some manufactures are still selling the granular form though. If you're using granular just be sure to scoop out the pooled blood before you pour into the wound. And pack it tight against the bleeder if you are able to locate it.
Also, people freak out about shellfish allergies and chitosan since it is derived from the shell of shellfish. From what I've heard this is completely false as the two proteins are completely different.