Any opinions on how these companies dedicated receivers and uppers compare to each other?

I have an Angstadt 16" carbine. I built it but use his internals.Shot a local carbine match this weekend and it ran like a sewing machine. No failures. Yes it costs a little more but it is high quality. Last round hold open works like a charm. Customer service is awesome. Always called me back or answered emails within the day. Can't say anything about the QC10 as I am not familiar with them but if I was going to by another, it would be an Angstadt Arms. And no, I don't work for them as I couldn't be that lucky to find a job I would enjoy.

When I was building mine Angstadt kept pushing the date back over and over.  Finally got impatient and went with a QC10 lower.  Since it works like a charm, I havent looked back at Angstadt.  I went with a Matrix Arms Side Charger as I wanted something different.  Love that side charger.

I have a QC build using a QC lower and Gibbz side charging upper and love it. Zero issues.

Good to hear a couple opinions both ways. I was also considering running a side charge upper just to see how they worked.

Side charger will be next.

I also have the AA, and its a real high quality set it runs like a sewing machine too, although my LRBHO isnt working.  Ive been meaning to email Rich about it, but i havent gotten around to it yet.  Im sure i just have to tweak it a bit.  

Did yours work right off the bat Richie?

Give me a call. I sent you my number. I had a mixture of parts but once I got his buffer,spring and spacer, its all good!