Natsu is not stronger than laxus. Natsu is simply allowed to beat the main antagonist because he is a main character.
Poor Natsu, he can even become a God and beat Zeref but he still will be weaker because "he is main character"? Natsu taking on most powerful guys doesn't make him neither stronger nor weaker than Laxus or Gildarts. Let's stick to the facts, not biased opinions. Why Mashima chooses Natsu to beat the main baddies doesn't really change his powerlevel, does it?
That's why Laxus, Gildarts and Makarov mostly sit out fights so Natsu can shine, and when they do face similar enemies, they outperform him.
Full powered Laxus lost against
Lightningless and
Dragonforceless Natsu+Gajeel.
Similar enemies, eh?
Jellal vs Jura. Jura's was shitting his pants seeing Se-Ma.
Laxus vs Jura is a very close win for Laxus
Natsu in dragon force vs the same Jellal who could take on Jura, that is on Laxus's level is a ohmygawdstomp by Natsu.
So power levels are something like
*Laxus=*Jura+1
*Jellal>>*Jura
*Natsu>>*Jellal
Yeah, I am using A>B>C logic. Jellal is like one of the fastest people and Natsu didn't even give a shit. Laxus's speed wouldn't be a problem for DF Natsu. Natsu's flames also incinerate everything, including magic. Natsu casually BURNED Sting/Rogue's Unison Raid, Gajeel's steel skin and Sting's stigma.
Oh, that's all not taking Lightning Flame mode into account. The only card you can play is "Laxus trained since then so he's stronger!", but you can't prove it :<
I'm using DF Natsu as a reference because he can casually go into Drafon Force now, unlike Laxus, who wasn't able to do it. It MAY be a result of his training after the timeskip, but I highly doubt he will be ever able to use it.
Remember laxus has never even used dragon force and he is this powerful. Laxus also decided to get stronger over the timeskip. He was one of the few who explicitly stated that so there's no reason he didn't grow exponentially like Natsu.
Laxus is pathetically weak, you know? His power comes from lachryma implanted in him because he has no talent for magic and/or has pathetically weak body. That's a pretty big reason as to why he shouldn't get as huge power-up as Natsu. His power is not really his. There's a limit on how much he can take from that lachryma, right? It's also a reason I think 2nd Gens can't really use Dragon Force. It's like comparing Juvia with a guy with a HUGE water blaster. Laxus just has a huge taser.
Also, laxus and gildarts are close in power. I did not say laxus is stronger. During the GMG, after jura's spell hit the magic counter, Makarov noted he is comparable to even gildarts and laxuw went on to defeat jura. That's enough proof.
And now, Natsu beat Gildarts's record in "Bluenote extermination" discipline without both LF and Dragon Force. He ended in with one attack while being pissed off at Chelia, while Gildarts took like 3 with being fucking crazy with veins that are not even there popping out. That doesn't give us real comparison, we just know both Gildarts and Natsu are stronger than Bluenote. But if speed of extermination is any indication, Natsu was faster with barely like 1/4 of his power. And we have aura melting whole stadium. Laxus was fighting seriously against Raven Tail yet his powers weren't so overwhelming to have affected whole stadium. It wouldn't be a stretch to say Natsu is already on Gildarts level. Yeah, without LF and DF. Even if Gildarts's powers are this strong those 2 powerups can easily close the gap.
I just can't see how Laxus can compete. Even back in GMG, imagine Natsu in LF mode. I'm pretty sure Natsu in LF or in DF could exterminate whole Sabertooth if not for Minerva. (Yeah, using my favurite A>B>C, powered up demon Gemma killed by Sting and Rogue, stomped by base Natsu).
If Natsu could IMO take on Sabertooth in LF mode, then Raven Tail wouldn't be a problem.