John we use 100' 12 AWG store bought cords and while they are not as tough as some of the rubber cords we could make they do have some advantages.
One thing is they are not as heavy when wrapping them up.
Another issue is the store bought cords are much more slippery which makes a huge difference when dragging them around corners.
100' of rubber 12/3 cord can be a real pain to untangle.
I do have a 100' of 10/4 heavy rubber cord that has a twist lock (L14-20P) on it that fits most generators on the other end it has two GFCIs one from each circuit and each of those feeds one duplex.
I find this handy to keep the generator far away and have two circuits with a total of 8 receptacles, I used 10 for voltage drop and because I had it.
Construction & Maintenance Electrician