I can think of only two advantages that PC has over PGII:
1. Air play, PC not only introduces the medium/heavy bombers that can be used "strategically" but limits aircraft loiter time/endurance requiring them to RTB to refuel.
2. PC has operational movement, train, and air and naval transport.
The Two major disadvantages(?) are:
1. PC completely revamps direct attack resolutions combining assaults and "stand-off" (1 and 2 hex) attacks into a single 0 hex range attack. Depending on the terrain, the attack will either be resolved as an assault using "close defense" values, or using "initiative" (ranging) stand-off attacks. Also, massed attacks are resolved by adjusting the defenders initiative down based on number of adjacent attackers . Range 1 or more attacks are always "indirect" artillery attacks.
2. PC has a core unit limit (like the PGIIIs) that forces the player to concentrate on the best "bang for the buck" (prestige); i.e. tanks, pioneers, artillery, fighters, and tactical bombers.
- Mounted infantry do not immediately dismount after being attacked
- There is no "combined arms" mutual support between adjacent units of different types; except AA and arty
- Towed artillery can move AND shoot (okay for =< 75mm/3 inch but not bigger stuff)
- Self-propelled artillery can move then shoot at max range
- Artillery can only provide "Final Defensive Fires" (aka defensive fire) to immediately adjacent units (vice their full range)
- Max range for vurtually all "regular" artillery is 3 hexes
- AA arty can move and shoot aircraft