Originally posted by SilentHunterKellen
If you want strength go aluminum but graphite is pretty sound.
Seriously, aluminum is ONLY for show(In critical places)...
I've bent more aluminum parts on the 4-tec than I can count... Rear shock tower bent the first time I hit a curb, the graphite replacement ran strong for over a year. My front knuckle's gave out twice(Within the first week), the right rear bearing carrier SNAPPED in half, the rear gear-box stripped out(In three places, and I was NOT trying to overtighten anything). Needless to say, I will NEVER buy anything from PowerLine again. It's expensive, and, in my experience, not as durable as it's made out to be.
Aluminum is good for places that wont be subject to much stress, or immediate hits(IE, curbs, poles, parked cars).
I've since been converted into an anti-aluminum Rc'er. Graphite all the way.
Graphite (Like eddy said) will not flex, and it just looks cool.