Top down or "in place" drying is another popular option for drying. The pro's are you only have to disengage a small corner of carpet to check for a porous carpet cushion so you are less likely to damage the carpet or seams when handing a wet carpet. In place drying requires more drying equipment and less labor so it is more profitable.
The cons are you are not getting warm dry air to the carpet cushion so a thorough extraction of the carpet and cushion, increased vapor pressure differentials between the wet material and ambient air, as well as the sub floor temperature well above dew point are crucial to successful in place drying. In place drying usually requires more equipment on the job and more effective equipment so your initial equipment costs are more.