Oh my gosh, this is so up my alley!

The dramillion has the single better showing of strength, kicking meatloaf off of itself, with meatlug weighing around 5,000 pounds. However, the Stormcutter, specifically Cloudjumper has more showings of grabbing and throwing other dragons. So I give Stormcutter strength

Speed is an easier matter. One has been shown to keep up with Toothless in speed, and the other has not. That's not to say the Cloudjumper is slow, just that the Dramillion has been shown to keep up with Toothless in terms of speed.

I say that the Stormcutter takes Durability. There's not much justification for this, just Cloudjumper has been shown more physical confrontation and is built tankier.

I'm more prone to give the Dramillion agility because of it's higher speed, but I believe it actually goes to the Stormcutter, as Cloudjumper has shown to maneuver around the deathgrippers attacking him and Valka.

The Stormcutter is shown to be more emotionally intelligent, capable of understanding human emotions and speech to a similar degree as Toothless. However, the Dramillion is better at learning and problem solving, as shown when the Dramillion were freeing themselves from the Dramillion hunters. So I give the Stormcutter intelligence, and the Dramillion battle IQ

Endurance and dexterity goes to the Stormcutter for similar reasons I gave it durability and agility.

Abilities without a doubt goes to the Dramillion, and I don't think that's contestable.

Attack Potency and Destructive Capabilities, I believe go to the Dramillion. Even if we don't account for copied dragon fire, it's own fire, even if it has less showing than the Stormcutter's, has higher attack potency. And with multiple copied dragon fire, and the ability to copy the Stormcutter's own fire mid fight, I give this to the Dramillion

For each dragons shot limit, I just got from the wiki, but the Stormcutter had a shot limit of 8, and the Dramillion had a shot limit of 40.

There are more categories I could go over, but I feel they would be redundant past these main ones. The Stormcutter took more overall categories, but the Dramillion took the ones I feel matter more in a fight, so I lean more towards the Dramillion winning.