Alongside the lesser bandits and outcasts, the brigand is far better equipped than the average no-gooder, having turned wholly to a life of pillage and general crime to make a living. Usually sporting aketons or white gambesons and shields along with maces, metal and wooden spiked clubs, occasionally hammers, spears and ranged weapon (either bow or crossbow,) they can pose a threat to novice and even moderately skilled players, often dehorsing them if they ride poorly armored mounts and swarming the downed fighter with their weapons.
They can be considered the basic foot soldiers of outlaw bands alongside the bandit. Those with crossbows are considerably more threatening, especially if you've been weakened and are on your last legs health-wise.
They are still not much in a fight against sufficently trained and armored soldiers and cavalry (often even novices like mercenary nobles and faction noblemen) will often literally run circles around them and tear them to shreds if they become too scattered. If you want to field these men, field them in large numbers and plant them on the highground where they can put thier ranged weapons to use. They can be rescued, recruited from prisoners, or trained from bandits, and sadly are a dead end, but are at least better soldiers than bandits or outcasts and able to stand up against sellswords and if they outnumber them, armsmen.