I'm not afraid to go with non-Canon brands, if they perform as desired. I don't have experience with the Yongnuo, so I can't comment on them, but I have heard of some minor issues. Then again, I've heard great stories as well.
I was coming from a Canon 430EX II, 580EX II, and Pocket Wizard TT5 setup. Everyone knows that was not a cheap setup, and supposedly was a top of the line setup. I had nothing but issues with it. Reliability issues, the AC3 not making adjustments correctly, flashes behaving erradically. I was unhappy for something that cost so much money.
I recently switched to the 600EX-RT and couldn't be happier. I have 4 of them, and they work exactly as they should, every single time. The only thing I miss is the physical dials of the AC3, and I wish canon would put out a controller with physical dials. I don't see the cost to be that big of a deal, as it was cheaper than my Pocket Wizard/430EX II/580EX II setup was, and performs better to boot.
So here is one vote in major support of the Canon 600EX-RT system. Not to take anything away from the Yongnuos.
EDIT: I guess I didn't address your specific use for them. For large reception halls, yes, I find the 600EX-RT's to be underpowered, but you will have that with any flash. That is more of a job for studio strobe. I have lit receptions with them, but I either gang them together, shoot them bare (For backlighting), or bounce them off of the ceiling. I don't really think they have quite enough just to light a big reception hall with just 1 inside of a light modifier. Still an excellent system.