AQR is offering products to those who are trying to diversify risk away from the index. There is no point then in comparing the returns to the index. To say the investors would have been better just holding SPY makes no sense when that is exactly what they are trying to not do.
I agree of course that the performance of for instance a neutral long short fund should not be compared to the market return. However, AQR still need to deliver a positive return sizeable enough to justify the risk. My question is: Have AQR on average achieved that? Are they worth what investors have paid for their service?