You cant hunt waterfoul with lead and it doesent retain energy as well.

Steel also has a completely different shot size numbering/lettering system.

Im with you, choke size is over-rated. For almost all IPSC stuff I use a light mod unless steel targets are way out there or set real heavy. For skeet and doubles trap I use a IC. Sportsmans Team Challenge I just use IC as the shots are pretty close in, but going the speed of heat.