For UKF I'd say that the top large team commanders have always been and probably always will be the ones with the Churchill Crocodile
Crocodile will do a lot vs Panthers, JP4 and Elefant, right
For USF which are probably the poorest Army to choose in a large team game
and large team games are dictated by Armor
No they're not. On the allies side, 4v4 is dictated by teamweapon spam, (lmg) blobs and indirect fire spam. And USF is amazing in all 3 departments.
Only for the axis it's dictated by armor as they
must decide the tank war in their favor in order to win a balanced match. And the Jackson is very important to defeat Panthers on non-open areas. (e. g. the forest in Lienne Forest or Essen Steelworks)