Hector VS Surtr:The Pinnacle and it's Conqueror's

Let's state something quickly here. This is objective, not subjective. I'm trying to show how, even with Surtr's bulk, he's not neccessarily over the top.

Okay, let's start with L!Hector (his best form for most content) then. A potent unit capable of avoiding doubles on offense or defense and able to double back. The most optimal build for him is:
L!Armads,Bonfire,DC bold fighter, Ostia's Pulse, QR3

His IV set can be optimized and it depends on what you want from it, but for general use and arena's sake, we'll go with +atk-spd.

Now, for Surtr, his IV setup is iffy. He can't drop his Spd or HP for scoring, so the best setup is +atk-res, though that hurts the bulk he has over Hector, he's still bulkier in the magic side of things.

Also his optimal kit depends on the unit's he's fighting. He has to be bulky if he wants to bait units into his range to use Sinmara to its full effect, but he will be a sitting duck without Wary Fighter. However for consistencies sake we'll give him Hector's exact build, since it's optimal for armors in arena 99% of the time.

Now, into the nitty gritty of things.
Stat comparison with optimal IV's at +10
L!H:51/64/24/45/30
Srt:54/63/21/47/34
The major differences are in res and HP, where Surtr has a total of 7 more magical bulk, but this isn't as huge a deal as it may seem.

Upon further inspection, and upon testing versus every unit ingame, with a multitude of builds each, I've come to the conclusion that Hector is still objectively stronger, and let me explain why.

On offense with these builds, Hector beats out Surtr because he has slightly more atk (1 point does help a bit) , and as such not everyone can kill him on retaliation. Out of 319 units ingame, each built 2-3 different ways totalling around 750-800 different builds, Hector wins out in offensive kills by 8 so not an incredible margin. (so Hector killed about 676 and Surtr 668)

Now upon testing these builds in enemy phase nets us a very similar situation, but one that's easier to see.

On Enemy Ohase, once more, Hector can and will remain the better defensive unit. Surtr kills 457 units, and successfully survives 162 and dies to the other 200 or so. Hector however, due to his omnibreaker, defeats 477 units (almost hitting the 500 bomb) and all but 30 units are left in weakened states, unable to defeat him.
So in pure numbers, Hector wins out by a slight margin in offense and a major margin in defense. Now, when we factor in Surtr's Menace, then and only then does Surtr win on offense by a fairly large margin. Hitting the 800 kill mark. This does however mean that Surtr must be within 2 spaces, and the enemy unit must be baiting him out, and this doesn't take into factor how Surtr doesn't have warry fighter and thus can't deny mages the kills they can normally attain (this also doesn't factor armor march, in which case you may never even procc sinmara or SMenace in the first place)

Now that you have numbers, let's talk how this should work in actual play. Maneuvering a armor unit is relatively complicated, and relies on Armor March to maneuver perfectly. This is further worsened by the fact that Surtr could be bursted down by a mage if he runs Warry Fighter or not, and as such, there isn't much difference than Hector in this regard. However, Hector's advantage is his ability to run 2 out of three fighter skills at a single time, and his ability to tank and kill most if not all units with minimal ease due to this exactly. Surtr can attain great heights, but one would need to preplan everything and maneuver the AI perfectly as to make them reach the 2 tile radius for Sinmara and Menace to be even usable, whilst Hector is consistent and will not fail you so long as you have allies beside him, something that Surtr can't do at all and must rely on chosing between Warry Fighter for bulk and utilizing his weapons at their greatest potential, or chosing the most common build and thus rendering his greatest strengths hard to activate due to his inability to tank a hit and keep enemies in his range.

Thus, Hector wins in consistency and still retains his spot at the pinnacle due to his omnibreaker and his ability to be as consistent as possible.