Well, i did as you said by making a splitscreen and threw the gernades at the feet of the other player.....
It makes no difference.....the effect the gernades have on you or another is EXACTLY the same.
But....i found out there is a difference between the AU frag gernades damage, and the non AU frag gernade damage. The AU frag damage are indeed a little more powerful.
First of all, you have to realize MC has health in halo 2 like he did in halo 1, the only difference is you cannot see the health in halo 2. Everytime you see blood when you get hit, your health goes down, and even once your shields recharge, you health does not, but remains lessened.
The frag gernades now not only take off all the shields, but take some blood (health) with it. Before no blood was let out.
If you throw a gernade right under MC's foot it will take all shields, and some health (blood). Wait for the shields to recharge, then throw another at his foot. Do this three times (for a total of 3 gernades), and it will kill him.
So, one gernade, when sheilds and HEALTH are full, will never kill MC.