Dabura's performance says otherwise.
In the few pages in which the combat between Dabra and the Saiyajin occurs, I observe a Son Gohan with more problems in dealing with the opponent than the opposite. Goku clearly says Dabra is stronger than they thought and that Gohan really slacked off. A the end of the combat, the fatigue seems to belong mainly to Son Gohan and not Dabra, whose posture is upright. Dabra then abandons the combat under the justification of using Vegeta to awaken Boo and later, when asked by Babidi if he could in fact defeat Son Gohan, he says "yes" and then says he can clean the trash. Dabura is not minimally concerned compared to Son Gohan's posture, who stress the fact of having to explode in rage to win:
If he was really holding back against Gohan, he wouldn't have felt the need to use his spit, something that would've ruined his goal of gathering energy from him.
As far as we know, Majin Boo receives the energy taken out from the good guys, and a form of taking it out is damaging them, hurting them. Being transformed into a statue and smashed to pieces could very well be considered a form of dealing damage, why not? If we assume it isn't a form of dealing damage, then you'd be saying me Dabra was pretty desperate by using such one shot technique, which isn't right no matter how you look at it.
Dabura is simply arrogant.
Still we don't have someone contradicting such confidence from Dabra, on the contrary we do have a pretty worried Gohan, remembering hid dad's incentives words for him to get angry, which solidifies he wouldn't be a match for Dabra otherwise.
I used to believe Gohan had an advantage over Dabra, specially when there's a guidebook named "Dragon Box" that says such thing, but that's not really what we get when analyzing the whole thing and looking at the dialogues.
The art clearly goes against it too.
While there's clearly a lack of spark aura, Gohan has only one strand of hair falling over his forehead, while Gohan showed that two strands of hair is a characteristic of a simply SS1:
Furthermore, Gohan makes note of telling Kaioshin that Goku and Vegeta were fighting at a level beyond a Super Saiyan, heavily suggesting he wasn't doing the same against Dabura.
Gohan making note of other people using SS2 does not exclude him from using it though, nor do I see how that point makes any sense. What doesn't make sense is Gohan showing the ability to go SS2 at will in the Budokai and not doing it against an enemy who is clearly giving him a lot of troubles and is potentially >> him, specially when he can save his friends' (two best friends, might I add!) life by taking out such enemy.