Almost every house I do that is over 3000 sq feet and has mostly electric appliances usually needs a sub panel. I think the NEC needs to approve a 200 amp 50 or 60 circuit panelboard for residential applications.

One very important thing to keep in mind is that subpanels help reduce the length of branch circuits and thus reduce voltage drop. If you are installing the subpanel right next to the main panel in a new house then you are doing yourself and the customer a disservice. In new construction, subpanels should be placed on a different level and/or a different end of the home (relative to the main). Make sure one of the panels ends up close to the more heavily loaded areas like the kitchen. In an existing/fully-finished home, placing the sub next to the main may be your only reasonable choice.

I don't believe voltage drop is a real issue in many homes but a competent electrician still must take the issue into account. Having 200' long branch circuits in a home is something to be avoided!

Can you name even one case when you are going to use 50-60 circuit spaces feeding branch circuits in close proximity to the panel? If the loads are farther away then a subpanel is in order anyway.

Have you done load calcs on the larger homes? Are you sure 200A is adequate?

I think triple has some good points on the voltage drop issue.

I will add that I am not in a hurry to see 60 circuits brought into one 14" W x 3" D enclosure.

If that was all two wire circuits that is 180 conductors, IMO it would be tough to keep neat.

If it is a case where 200 amps is enough power and you can locate the panels side by side get one panel Main breaker feed through style and get a second 200 amp main lug only panel.

Nipple them together with a couple of 2" nipples and for all intents and purposes you have 84 circuits in 'one' panel.

Bob