I'm not sure what the terrain is like in Malaysia but if you ride huge hills, a 8" rotor is a really nice to have. I agree, as mentioned by other folks, that the advantages are more stopping power, less heat buildup and ultimatly longer brake pad life.
Below is a pic from the Jumping Pond Ridge/Cox Hill in the Kananaskis area of the Canadian Rockies. I can't image the desent with anything but 8" rotors. One of my riding buddies cooked his pads on his 6" Hayes mechanicals this day.
Cheers
T.J.
On the way up....
Shamless bike porn
The beginning of the descent
EDIT: If you are seriously considering 8" rotors, be sure to check with your fork manufacturer to be sure it can handle the added forces. Some forks are not rated for 8" rotors (I.e. All Fox <04, most X/C forks...)