I made a post here comparing some of the physical and electrical differences of residential and commercial fluorescent ballasts:
https://www.lighting-gallery.net/gallery/displayimage.php?pos=-264949

What other differences are there? The residential ballast says nothing about thermal protection on it so I am thinking that might not be present there. I hear that 48" F25T12s can only be run on residential ballasts, is that because they normally underrun F40T12 lamps?

The commercial ballasts generally have copper/thicker aluminum windings so they don't heat up as much.
Most of them are high power factor, because commercial/industrial customers get billed for power factor as well.

The reason a F25T12 cannot be run on a commercial ballast has something to do with the capacitor. It is the same reason
you should not run an F34T12 on a commercial ballast. It will make it overheat (or at least run hotter). If you run
an F25T12 on a commercial ballast it will also run at full 40W power.

Here's a discussion about the F25T12 lamps: https://www.lighting-gallery.net/gallery/displayimage.php?album=7829&pos=14&pid=253074

Yes, I did notice that the aluminum windings on the one I disassembled looked pretty thick. I don't think iot did much though because the top of the light fixture when running for a while was still too hot to touch.

So essentially both ballasts run lamps at similar power, but since the commercial version is CWA (more constant-current than HX) it will overdrive energy saving lamps. Very cool.