I love ours. I would rather have the extra counter space than the old style one. The grates are a little tippy, but I have a $$$$ stove in the sticks & brick that does the same darn thing! And they are heavy duty cast iron grates.... go figure.
I always use a large pan on one side and a smaller sauce pan on the other.
I just walked outside and measured for you. My round 10" cast iron griddle fits perfectly on one side and then my small tapered sauce pan - 5" bottom, 7" rim fits nicely next to it. You could go a smidgen bigger.
So my largest pan is 10". I actually looked and I don't even own anything that's as large as a 13" pan in my house. I'd use my outdoor stove for anything that large anyway b/c I don't want the condensation and splatter in the TC.
13" would overhang into the other burner.