It really has to do with how your individual gun patterns with the size/s of shot you're using.
That being said the old saw is pretty accurate that "Steel Shot patterns 1 choke TIGHTER than Lead shot" .
AND another thing is that chokes tend to pattern TIGHTER as the pellets get larger.
So, while you may like how your gun performs with a Full Choke with a medium sized shot, you may find that it patterns the same using a Mod. Choke using large shot sizes.
Steel shot for geese is generally pretty large stuff and often it will pattern well with a Mod. or Imp. Mod choke instead of a Full.
While Large sized Lead shot's patterns can actually "open up" using too tight of a choke, the risk of running too tight of a choke with Steel Shot in a fixed choke barrel is opening (swaging) it up, or in the case of screw-in tubes distorting and jamming the threads, sticking the choke tube in the barrel.:smash:
Lots of people handicap themselves by shooting too TIGHT a choke (and a smaller sized circular pattern) at close ranges.
For hunting Ducks over Decoys I like Imp. Cyl.
For big Geese I usually use a Mod. choke with 000 Steel Shot.
:cheers: