Question about Roman units

[Aemilius Paulus]

The Polybian Principes have sword attack. The Camillian Principes have spear attack. The spears get a -4 attack against sword infantry. So your Reformed Principes actually have a much lower attack against cavalry, but a little higher attack against infantry. Polybian Principes have 11 attack vs infantry and 24 armour. The Camillian Principes have only 10 attack against sword infantry and 14 against cavalry with only 22 armour.

So the Polybians are better since the vast majority of the units your enemies field are foot and not mounted. For the few cavalry that you will have to face you can just bring some Triarii. The Polybian Triarii are actually worse than the Camillian. They have 2 less armour and the same attack.