I have owned power amps from QSC, Crown, and Peavey. All of them have been quite good but...
I have 3 reasons for picking QSC.
I chose QSC becuase I have had a dozen + of them over the last 5 years (PLX ,RMX and recently a GX5 model ) all of them have been great performers, excellent values, durable and trouble free. They became the primary amp in all of my PA systems and I eventually ended up with all QSC PLX and RMX amps and a couple of Crowns that would have been replaced with QSC PLX models when it came time to retire them .
The Bob Lee factor is the second reason. He is a regular poster here on talkbass and adds to the support of their products.
QSC gives you a six year warranty. Crest doesn't do that.