I dont like considering Gon san a character because its just a form that Gon takes on and from what we see he really doesnt have too much controll over it but lets just look at Gon san's power for a moment.
We saw that Meruem (pre rose) is insanely strong even before absorbing life energy from youpi and pouf but im curious, i wonder if Gon san could be put on the same level. When Meruem hit Pitou in the face on the farm he said it was meant to kill her, im not suggesting he was going all out or even using any aura in the hit but even when he did the same thing to pouf he sent him through a wall. When Gon san and pitou fought i believe (correct me if im wrong) he killed her in two hits, a kick and ja-janken to the face. I dont think that Meruem could have done the same so quickly, im not suggesting he couldnt kill pitou, no that would be easy for him but all the same, even with two hits, one with high concentrated aura, i dont think he could kill her. However just because i say this doesnt mean Meruem is weaker, remember, Gon is an enhancer while Meruem is a specialist. Naturaly its MUCH easier for gon to concentrate his aura into a hit like that but it still raises the question, who is stronger?
Personaly I still dont know though I'm leaning towards Meruem, comment and tell me what you think.