Bear in mind that Polybian units have higher morale than Camillan units Hastai P/13 to C/11, Princepes P/14 to C/12, Triarii P/15 to C/13, Marian Cohors Reformata are M/15.

Caveat; According to the Akriades cards for EB1.0 some units statss have changed in 1.1

Also remember that to begin with you will be comparing veteran Camillans with raw Polybians, I've always found that with some experiance Polybians are much tougher and will stay in melee a lot longer.