727 deep steel pan

A deep cast aluminum pan hanging down there is much more likely to be damaged by road hazards. On top of that, a cast aluminum pan cracks or breaks (leaks) where a steal pan will dent (not leak) when struck by said road hazard.

Many transmissions have been ruined by the owners decision to install a cast aluminum pan

LOL, my headers hang down lower than the pan.
The alloy pan will seal better for obvious reasons.
And there are claims that the more rigid design helps reduce trans case flex. You can stick a temperature sensor in them.Better heat disbursement, blah, blah.