Gohan was a SSJ
The most undenieable argument someone will use to defend it is the art. Gohan was clearly portrayed as a SSJ looking just at the art. The first appearence of a SSJ2 in the manga was through Gohan in the Cell Games, which was described in the Daizenshuu as a SSJ2. He had a spikier aura and sparks on his aura for 90% of the time. It disappeared, although for a very short while and quickly reappeared after and some of the panels he didn't have sparks was even due to the absence of aura, and as many argue, the sparks are a trait of the aura, they happen when the aura is on, and no aura, no sparks.
So clearly constant sparks, and the fews panels he doesn't have it are easily overshadowed by the ones he constantly DOES have it. Saying we can't really say the sparks are a trait of SSJ2 because they aren't present through 100% of the time and are rather present through 90% or more of the time is a logical fallacy. Even more when we might have a confirmation that an aura with sparks and one without one are a clearly differentiation between SSJ and SSJ2 for the author himself, who makes this point through Goku himself differentiating SSJ and SSJ2 before Babidi:
Some people use Babidi's line in the next panel as a way to invalidate the argument, though what Babidi really says is "ridiculous transformations... there's no great change, is there?", which just means SSJ2 doesn't look too different from SSJ, not that there's no difference at all.
Gohan against Dabura is clearly missing those SSJ2's traits. He doesn't have sparks for ANY moment (which isn't cmparable with missing it for very few panels), and whilst one could argue he does have the hair as a SSJ2 trait, he also displayed a hair with one strand when transforming against during Videl's beatdown, when he was 'almost undeniably' a SSJ. So the hair can easily be argued as an art change, or just a small oversight from Toriyama -- yeah, missing one strand of hair is way easier to be looked upon as an oversight than missing a way clearer trait like the constant sparks --
Even when SSJ2 was already kind of 'outdated' and overshadowed by the SSJ3, Akira Toriyama still made a point to detail Vegeta's aura against Kid Boo with sparks, also only missing it for very few panels.
Also, concerning the narrative/the story, there're some points one could use to favor the SSJ side as well. Vegeta states he'd defeat Dabura and pretty much considers that level Gohan and Dabura fought at as a very low one -- Goku also agrees, although in a less 'arrogant or straight way' -- yet Goku doesn't suspect Vegeta had SSJ2, as seen by his surprise when Vegeta transformed:
Majin Vegeta SSJ is also arguably treated as a bigger deal than Dabura. One could say Dabura was expecting him to make a better job because Gohan would have to be fighting against a 'friend', hence not fighting at his fullest. But it still would be pretty much stupid for Dabura to choose someone weaker than him as that someone wouldn't be able to deal damage to Gohan, seeing as himself could barely move the damage meter when launching a very powerful attack. You could say Dabura doesn't know how strong Vegeta is, but since he could say there were three people with exceptional power hiding behind those rocks, it's understandable he'd also manage to gauge Vegeta's powers when seeing Babidi push it 'out of him'.
Gohan was a SSJ2
The mojority of people who support this will use the narrative as a flat out indicator of Gohan fighting in SSJ2 against Dabura. First thing would be Goku comparing Dabura with Cell and later stating he's way stronger than thought. Well, even if you think Goku meant the Cell he fought, he later stated that Dabura's way stronger than thought, and as many would argue kid Gohan wasn't stronger than suppressed Cell -- had only a speed advantage -- let alone MUCH stronger. Yet, Gohan could stay pretty evenly with Dabura, and was barely damaged from his blast. Since Gohan was stated to be way weaker than his CGs self, him staying somewhat even with Dabura doesn't make sense if he were using a form as low as SSJ.
--> Gohan barely damaged upon receiving a blast from someone way stronger than Cell.Yet, Goku made clear in the Cell Games Gohan's anger was the only way to beat Cell... Gohan's current power was nice and all, but the anger was da real s***. Even Gohan stated that now he sees what Goku was planning since the beginning -- Gohan getting angry -- and that that is the way to beat Cell. So, a considerably weaker Gohan going toe to toe with an opponent like that doesn't make much sense if he is using just SSJ.
Vegeta is also very impatient over Gohan's struggle with Dabura, saying Gohan was stronger in the CGs and that Dabura's not an opponent he should have this much problem with. Again, without even making reference of a form that Gohan used minutes ago that would undoubtedly defeat Dabura, if Gohan was a SSJ1. Not only this, but Goku establishes that Gohan has to get angry like in the CGs to triumph in the fight, pretty much emphasizing Gohan's hidden powers. If Gohan was a SSJ1, shouldn't be saying "do what you did at the Budokai" suffice here? Since Dabura would be pretty much easily defeatable by Gohan SSJ2.
Kaioshin also pretty much parrots what Goku says:
Kaioshin saw Gohan SSJ2 at the Budokai and even considered the possibility of it not being his full power. It wouldn't make sense for Kaioshin to urge some hidden power out of Gohan he heard from Goku if what he saw at the Budokai were already enough to get the job done.Chapter: 460 (DBZ 266), P10.2-3
Context: after Boo seems to be dead on arrival
Kaioshin: “Goku and Vegeta are probably having a roughly even fight…I’ll pin Babidi down. After that, if you can manage to defeat Dabra, then Babidi’s scheme will be completely wiped out! So then! Now’s the time to get angry, like Goku said! Get angry and show me your true power! Gohan, peace is almost at hand!”
Furthermore, you also have Kaioshin telling Kibito that what he saw from Gohan at the Budokai wasn't his full power, meaning Gohan had to have showed more power after the Budokai (or Kaioshin thought that way).
This is directly linked with Kaioshin stating that what Gohan showed at the Budokai might not have been his full power:Chapter: 470 (DBZ 276), P5.2-4
Context: Kaioshin says the situation isn’t completely hopeless
Kibito: “Huh…!? You can’t mean…Does this have anything to do with Son Gohan…?”
Kaioshin: “That’s right…His power is far beyond our imagination. If we took it and changed it into something even more unreal, he might be able to surpass Majin Boo…”
Kibito: “Wh-what!? That can’t be…”
Kaioshin: “You didn’t see how amazing those 3 Saiyans were, so you probably couldn’t imagine…”
Chapter: 471 (DBZ 277), P10.2-4
Kaioshin: “I want Gohan to use the Z Sword to defeat Majin Boo. Knowing him, he should definitely be able to use it.”
Kibito: “A-are you serious, Lord Kaioshin…?!! There’s no way that some human would be able to use the Z Sword!! That legendary sword which not merely myself, but numerous Kaioshins were utterly unable to handle…”
Kaioshin: “You were dead, Kibito, so you didn’t get to see Gohan here’s unbelievably tremendous power.”
Another nice point is Gohan tiring out and needing a Senzu Beam after Dabura's battle, simply because he had used a lot of stamina:
Yet, this goes against the main advantage a full power SSJ is supposed to have, according to Goku:
The regular SSJ was conditioned to minimaze the strain on their bodies during battle:
Daizenshuu established that what was initially shown from the battle between Gohan and Dabura was its beginning, and Gohan didn't make use of chi blasts, didn't take much damage from Dabura's blast, anything that'd deplete his stamina, unless he was in a form he had no full control over/wasn't trained to minimize the strain during battle -- SSJ2.
I can later offer some counter arguments to both sides (yeah, I have some points that might as well counter the narrative being so directed towards SSJ2, mainly counters towards the SSJ2 POV), but I think I'll just let you guys with the points concerning the two sides now.
