Both of these are point forward, and so one would assume that Longa has the advantage here, because it is the most extended blade, however it has the same distance to travel as Porta di Fero Mezana. This means that Longa is not in fact more extended then Porta di Fero Mezana. More extended also means, closer. That's why these two posta are contrary.
If Longa attacks Porta di Fero Mezana with a cut, Porta di Fero Mezana retaliates with a sottani deflection, stepping off the line and return with a Fendente to the arms. If Longa attacks with a thrust, then Porta di Fero Mezana will break the thrust, and return it's own.
If Porta di Fero Mezana thrusts or cuts, then Longa can traverse, and cut, or directly wound the arms. Which Longa chooses depends on circumstances. If Longa can, the fastest thing to is to directly attack the arms, and then step off the line. Most of the time, sidestepping the blow and returning a cut of it's own is better.
Longa really needs to probe against the other wards, and get them to make a mistake, and then retaliate. This is also true vs Porta di Fero Mezana. This companion ward can easily stop anything Longa tries directly. This means being somewhat more active the Porta di Fero Mezana. Porta di Fero Mezana on the other hand needs to be patient, and invite Longa to over commit on a probe, or to actually attack. If Porta di Fero Mezana attempts to move to early, then Longa will deceive it, and win.