''In contrast, Dante has trained and tempered his own Devil Trigger to the point where he can absorb the souls of powerful demons and bind them to Devil Arms (Vergil is capable of this ability as well, thanks to fighting demons and being hardened by experience just as long as Dante). He can also restrain his demonic power from drastically affecting his appearance...while Nero is stuck with his demonic power manifested in the form of his Devil Bringer arm.''
Dante's ability to absorb demons into devil arms does not have anything to do with his 'experience'. Dante was always able to absorb demons into devil arms - he did it in DMC3 too, when he didn't have a devil trigger yet (e.g. after fighting Cerberus). So training with his DT has nothing to do with it. Nero also seems to be able to do it, but he absorbs things into his arm. Nero might be able to create weapons out of souls just like Dante... he just didn't get the chance in DMC4 because he didn't kill any bosses that could be converted into weapons.
Dante can restrain his demonic power from affecting his appearance because he's half human. His normal form is his human form, and his demon form is a transformation. We don't know why Nero has a Devil Bringer arm, so there's no use in speculating that it's his 'demonic power manifested'. There has never been any indication that demonic power needs to physically manifest itself in Nero or Dante. So... that's just pure speculation on your part.
As for the question, at the end of DMC4, Nero is probably nowhere near Dante in terms of power. He was so weak to Dante that Dante actually toyed with him... so why would he be equal to him at the end? He did gain the help of Vergil (or his soul, I should say), so his Devil Trigger could be very powerful... but probably not even half as strong as Dante's Devil Trigger. Maybe if his DT were to absorb some powerful stuff, he could become as strong as Dante. We haven't seen him absorb much yet, after all.
Also consider that if Vergil was his father and his mother is human, Nero is only 1/4 demonic. Since humans are pretty much helpless against demons, Nero's base form must be fairly weak.
So no, Nero does not equal Dante in power at any point.