For game pieces like this year's boulders, Aerial Assist balls, and even the balls from 2012, I think the notion that catapults inherently shoot more repeatably than wheeled shooters is a myth. If you're trying to launch a Lunacy moon rock or one of last year's recycle containers, then yes, a catapult is probably your best bet. But without more data directly comparing the catapults and wheeled shooters teams have actually built, I don't think anyone should be making confident claims to this effect.
Here's some slow-motion footage of one of the shots we took with our shooter prototype to test repeatability:
https://youtu.be/lQUPcOZiL3c (one-wheeled shooter with a curved hood and 2" of compression. The hood on this prototype went through about 60 degrees of arc I think.)
The blue dots on the board represent where previous shots landed. As you can see, the consistency is as good or better than what we needed to make the shot from the outer works, and this was without even running closed-loop control on the wheel speed.