For the most part, the Border Worlds' fighters seem less finished and refined compared to the Confed craft: the Vindicator's got all that junk stuck onto it (torp hardpoints, missile hardpoints, special Leech Guns and Stormfires), and the other two look almost primitive compared to the Arrow, Bearcat, and Excalibur. The T-Bolt's a bit chunky, sure, but most of the Confed fighters seem to have been designed for front-line combat, to judge by their equipment and weapons loadouts.
If anything, they're more reminiscent of the whole 'Ferrett stuck onto a corvette engine' that we read about in End Run than even the militia or pirate fighters we see in Privateer.