It depends on the application.
The ideal place that I can see using them is in a very short barrel(less than 9") that has a very high, short pressure spike. The use of a pig tail gas tube will tame the gas spike down, but the due to the the gas pulse still being short, and the gas port being very large, the extra power spring will prevent the extractor from popping over the rim during the violent cycle.
The disadvantages are that extra force of the spring on the extractor may shorten it's life expectancy due to the added tension that must be overcome to allow the extractor to glide over the rim for engagement.
P.S. The SBR(9" and shorter) that functions with a gas system is a conundrum in it's self. What started off as a 20" rifle that had variances built into it, has been stripped of these variable tolerance. By adding items such as a pig tail gas tube, heaver buffer, and stronger springs, you soften the gas pulse/bolt unlock time, and allow the SBR to function.