I've got a few of them. One rack I have 3 QSC PLD 4.5s. The sister rack has 3 Crown iTech 5000HDs. On paper, in 2 channel mode, they are pretty close spec wise for continuous power output. However, when I use the Crowns, I seem to get quite a bit more punch from the system.
The advantage of the PLD is that they are 4 channel amps and have great flexibility in their configuration. They are lighter weight than the Crowns as well. Also, the on screen display is much easier to configure the unit than the Crown. (unless you are just switching between presets, and in that case, it's a tie)
The huge disadvantage of the QSC is that they use USB as a communication protocol instead of Ethernet. This makes remote monitoring and control a royal PITA. With the Crowns, I can use my iPad to monitor the amp, or my WIFI connected laptop to adjust the configuration. (windows only though, which BLOWS) For the QSC, I need to have a computer at the amp rack for monitoring purposes. Lame. I did rig up a USB to Ethernet kit with a raspberry pi that sort of worked, but was less than desirable in the performance category.