The only difference we know with the Keldon between the Galor is that the Keldon is stated to be faster at warp, nothing else. It's hull shows two extra impulse engines, but since superior sublight performance wasn't mentioned it might mean the extra engines are only to compensate for the pod weight. We also have no idea what the pod really is.
Here are some obvservations from DS9: "Defiant".
- "Defiant"
Thomas Riker: It looks like we'll have to fight our way to Orias.
Kira: Listen to me... Those three ships up ahead are going to lock onto our neutrino leak and open fire, that means you're going to have to fight back. (the Defiant is cloaked, but the leak means they can't sneak past)
Thomas Riker: With this ship it's going to be a short fight, I promise you that.
Kira: Let's say you disable, or even destroy those three ships up ahead of us, fighting them at all is going to slow us down, then those ten ships behind us are going to catch up, and not even the Defiant can win against those odds.
Thomas Riker: We have come too far now to quit.
Kira: You are an experienced Starfleet officer, Tom, analyse the situation. Going to Orias is suicide. Now, the smart move is to make a run for it while we still can.
Thomas Riker: Maybe that's what an experienced Starfleet officer would do, maybe that's what Will Riker would do, but it's not what I'm going to do! I'm going to continue the mission.
-- Riker believes that fighting 3 Keldons is an easy fight, Kira doesn't disagree. It's having to fight ten Galors that is the problem.
-- Riker doesn't deny that fighting 10 Galors is suicide, but he doesn't see a way out of the situation until later.
- "Defiant" fight
- (Man: Took six hits on the port shields. There's been some minor damage to the outer hull but all systems are operational.) - In reference to shots taken by the Defiant from Cardassian ships, probably Galor Class.
-- Thomas Riker: Tough little ship.
- 1 hit, probably from a Keldon (Man: We've been hit on our starboard shield.)
- 7 main beams from a Keldon - (Unknown: Shields holding.)
- (Thomas Riker: Quantum Torpedoes, full spread. Fire.) 4 quantum torpedoes fired, the first two explode in proximity, the second two hit the tail and appear to disable power and maneuvering of the Keldon. (Helmswoman: Their defense systems are off line and they lost main power. The ship is out of the battle, now.)
- (Man: Three more cruisers just arrived in the Orian system. That makes five ships ahead and ten behind.) Riker still wanted to fight, but finally realizes the odds will only get worse, so he takes the surrender bargain to save his crew.
Keldon Class Cruiser
- 3 beams from Jem'Hadar Fighter (third hit blows up the small bow saucer) - disabled - "The Die is Cast"
- 18 volleys from Defiant in 3 seconds - only 3 volleys at the very end appear to actually hit - The Keldon being a cruiser is mentioned at least once in the episode. - (Unknown: Direct hit on the Cruiser's port nacelle. Their shields are down by 30%.), there is a significant explosion on the last hit that causes the Keldon to veer out of control. - "Defiant"
-- Each volley did 10% damage to the shields, assuming it was only 3 volleys that hit.
- (Thomas Riker: Quantum Torpedoes, full spread. Fire.) 4 quantum torpedoes fired, the first two explode in proximity, under the ship, knocking it around a bit. The second two hit the tail and knock the ship hard. (Helmswoman: Their defense systems are off line and they lost main power.)
-- If we take it as all equal, then the Quantum torpedoes were 2.5X stronger than the Defiant's phaser volleys. That doesn't even take into account that the first hit was in proximity by several tens of meters, which would greatly reduce its damage, meaning its yield is higher.
- (Gul Dukat: Those are faster than any Keldon Class ships I've ever seen.) In reference to the Obsidian Order ships at warp chasing the Defiant. The Galors were shown to be equal to or slower than the Defiant, since the Galors were never able to catch up to the Defiant in a straight warp chase.
It has to be noted that those Obsidian Order Keldons were only faster than normal Keldons, and they still didn't actually catch the Defiant until it stopped. For all we know, a fast Keldon may be slower than a Galor, and we're left still not knowing what the dorsal pod is about.
If anything, considering we see Galors, not Keldons, at the very end of the show, it's the Galor which should be late-refit Excelsior strength. One reason I like this is the Galor is 25% larger by volume, that makes it less potent for its size, although, the Galor seems to have a giant shuttlebay for its size. The ship is probably intended to conduct planetary invasion and ground support, for controlling unruly colonies.
The power balance should be pretty relative, too. That main phaser means the Galor should have an extremely powerful hit for its size, while it's shields and secondary weapons probably aren't noticeable, except in the later Galor.
Back to the Keldon: I think we need to consider what the Obsidian Order does to determine what the pod does. They're a militarized intelligence agency. Their ships probably do data gathering along boarders, and that would make the pods highly sensitive comms, sensor, and electronic warfare devices with facilities for the crews for those systems. They aren't going to have huge armies, so they shouldn't be troop transport pods; and they shouldn't want to fight open wars, so they shouldn't be extra reactors or a shield system.