It depends on your needs and the size of the home. I know a couple with
a 7000 SQ foot home they have two 250 amp main panels. I was told 250
is the largest main home panels available but dont know if this is
true.

Frequently main entrance cable around here is alunimum, I would spend
the extra for copper from the meter can to the main breaker.

sounds like a big home have you included a standby generator for power
failures? thats $ well spent