Basic has only the native tree, and the troops have their native equipment.
Expanded has all items, which is reflected in the equipment of the troops.
Gameplay has less than half the amount of items from Expanded: the troops have the same tier items, but with less variety. For example, there are 5 different tier 2 armors per faction in Expanded. In Gameplay it's just 1, so the t2 troops from that faction use only that 1 armor instead of the 5 from Expanded.