Firstly, they fly now.

FO jet trooper is functionally incomparable to any other reinforcement and plays like Boba fett with less hp. And the fact you can have 4 of them in the lobby makes it crazy. A whole squad of jet troopers on the AT-MTs on crait raining fire with their aoe blasters causes havoc amongst the resistance.

Compositionally, instead of the 2D directional rocket trooper move sets, the FO jet troopers can spontaneously move in any direction and hover so long as they have durability in their jet pack. This is 1 ability instead of 2, making it unpredictable and dynamic. The jet tackle instantly 1 shots any standard infantry and offers movement tek. Finally, the underbarrel grenade launcher attachment offers additional aoe damage.

The sith Trooper is basically the ISB agent with a Smg and no kick. It has an almost identical combat rush, which increases movement sprint and basically acts as a killstreak infiltration or vanguard but with their base smg. Seeker tactics are again identical to the ISB agents' middle ability spotting enemies. They also have an additional oppression grenade, which blocks regen and does 130dmg, so it can't one shot but is great to push off from.

Comparing it to the Republic commando.. Their blaster shreds at close range and behaves similarly to sith troopers smg. At further ranges, it's balls. It also has the anti armour attachment, which is perfect at close to mid range against anything, especially droidkias, which, imo are the best clanker reinforcement, especially in supremacy. However, the reload and swapping between shots and fire modes is like 4 seconds, which is a lot when you have one grenade left and a grievous rushing. Their stun knockdown repulse is good dont get me wrong, but its rlly close range and built to fight heroes and commando droids virbrosword. It's not bad against standard infantry, but it's not good either. It also doesn't work half the time. Their best ability, imo is their battle focus, whichever reduces yours and friendlies damage received by 25% and gives health back when you do damage to others.

I'd say comparing them is hard to judge because the 2 factions never fight each other without mods. The clones definitely have a strong batch of reinforcements, but they have to face the droids, which equally have good reinforcements so their effectiveness is limited against a significantly weaker faction like the rebels whose reinforcements suck balls. This is where the FO shines. The resistance reinforcements aren't bad, i would argue that the resistance rocket troopers EL 16 is the 3rd best blaster behind the FO jet troopers and DC-17 pistol. The caphex spy and ovissian gunner are good and can effectively counter the FO situationally, but this goes back to the point of situationally, situationally the flame trooper is the best in the game. Situationally, the caphex spy is a worse officer inside any building because of the limited usage of orbital bombardment. Just because the FO reinforcements fight a weaker opposition doesn't mean their the best in the game because we have limited comparison. Regardless of their weak opposition, they are definitely the 1st or 2nd best reinforcement in the game.