The12" - 32cm are big and HEAVY, especially w/ the cast handles. They measure just under 12" across the top from outside edge to outside edge. One thing to keep in mind about these pans, though, is because the side are sloped and they are fairly deep, the cooking surface area is smaller. The 36cm pans are probably about 13-1/2" across the top. I'd love to have one for the occasion when I sear something really big, like two turkey breast halves at once, but for the most part the 32cm suites me just fine. I can do two lamb racks at once.
The 24cm is a bit small for me, but it's nice for things like breakfast for myself when I cook a single sausage, etc. I find it too small for eggs, omelettes, etc. That's where the 28cm come in. Perfect size for omelettes, searing a couple of steaks, chicken breasts, fish fillets, etc.
I have a ScanPan 12" that has low side walls that are very vertical and I use that often just because of the large cooking surface.