FS ships can do pinpoint-accurate FTL jumps across systems, and do them extremely accurately and far faster than Halo ships can do Slipspace jumps. Halo FTL also takes several weeks to travel to another system, whereas FS ships can do that in less than an hour. FS beams can also penetrate shields, so that's a blow against the Covenant. FS fighters also carry a lot more firepower than Halo fighters with their multi-kiloton warheads, and can go FTL inside a system, so a single FS destroyer can launch multiple simultaneous strikes against Halo targets in the same system, and the Halo ships may not even be able to detect the destroyer. And if things get too messy in one of the strikes, the destroyer can always do a subspace jump there and start beaming any hostile warships to death.
On the other hand, Hallfight would certainly be interesting if SPARTAN-II's were boarding the Taranis. Victory for the SPARTANs would pretty much require them to be properly equipped and use proper tactics. SPARTANs equipped with battle rifles and assault rifles wouldn't be very effective against Shivans, however if the SPARTANs had weapons like the Spartan Laser, M99 Stanchion Gauss rifle, and Gatling guns, then they might have a chance, although the best possibility of success for the SPARTANs would be to use Covenant energy swords and to charge the Shivans and then use their superior reflexes and agility to dodge the Shivan melee attacks and then use their swords' armor-ignoring qualities to slice the Shivans to bits.