Quote from Stoxtrader:
Curve is smoother, risk is lower, but return is lower. Also, although most of the time diversification (modern portfolio theory) works, during times of crisis formerly uncorrelated instruments suddenly become correlated, and you aren't diversified anymore, and precisely at the time when diversification is desired most. What you really need is diversification + hedge + know when to get the heck out of the markets and just go to cash. And hedging with options, again curve is smoother, but return is lower. There is a definitely a tradeoff there.