I don't get it, I thought the race was easy. I did it in the Bretonian Heavy Fighter (Crusader?). I've played it multiple times (I've replayed single player) and lost once because Hovis smashed into me (wasn't that illegal?) and I still almost came back. The thruster at the beginning helps, but only for about five seconds. Then go to cruise and don't use the goto command. And it is a scripted race. He flies slightly slower than you, so you slowly catch up in the first quarter. Then he takes several turns wider than he has to (same turns, everytime), and at the end he screws up and misses a gate or something and has to loop back. Thats where I pass him, every time.
I think that the light fighter vs. heavy fighter argument depends on the individual vessel. Whatever you do, don't try the race in a Defender: I kept hitting the sides of the gates because of the wingspan. In a Cavalier it's easier to be closer to the sides of the gates, which enables you to make a sharper inside turn to your next gate.
As far as the fighting concern (vs. the Rheinlanders): I was able to stay with a Cavalier from the point of entering Bretonian territory right up until the evacuation mission from the Order's home base. (At that point I switched up to an Anubis, which I still have.)
The whole trick is what the individual ships are configured for: the Defenders can't take a heck of a beating because they're only configured to go up against ships as powerful as the Liberty Rogues (plus the occasional Outcast). The Cavalier, on the other hand, is more powerful both in shielding and weapons because of the resident "locals" (a.k.a. the Mollys, Corsairs, and a handful of Lane Hackers out in Manchester): quite simply put, it's built for a tougher environment, where the strength of a ship means life or death.