Hmm.
A QSC KSub weighs 74lb. The K12 weighs 39lb, and the stack is about 4 feet tall. Max SPL around 130dB. Add a B3n, and street price in Canadian dollars would be about $2,700 plus tax.
A G-K Neo412 is lighter, at 90lb. Pair it with a Mesa Subway D-800 or a G-K Fusion 800, and you've got a rockin' conventional rig that weighs under 100lb. With the Mesa, price would be on par with the QSC/Zoom setup. Add about $250 for the G-K, which has an all-tube preamp.
The conventional rig is a little shorter and lighter than the QSC stack, but harder to fit into a small car. The G-K cab is easier to maneuver, since you don't need a dolly and you can do the tilt-and-slide to get it in and out of your vehicle. Either setup would be a two-tripper for most people.
At least on paper, the biggest advantage to the QSC setup would be if you double on upright, keys, and/or guitar- one rig to conquer them all.
On fly dates, there would be a small advantage to the Zoom, especially compared to the rather chunky Mesa, which would force you to leave a bunch of t-shirts behind...
I've never put a dB meter on one, but my gut says that the Neo stack would move a little more air when cranked. It would look more intimidating on stage, but also be a pain to squeeze into small clubs.
I expect that most touring pros would go with the conventional rig, but a weekend warrior might prefer the more compact PA setup.