Battle Starts
Ichigo: "Flexes his spiritual pressure"
Danny: "Gets his soul crushed"
Winner: Ichigo!
Pretty sure it doesn't matter if stats were unequalized, Danny has no resistance to soul crush so he dies immediately. Now if soul crush wasn't a thing and or Danny had some resistance to something like that then it would be an interesting battle, with both having some form of Accelerated Development or Reactive Evolution that would allow them to keep up with each other, as well as other stat amp methods to counter any of the others added buffs.
Ichigo has better close combat skill and a sword, instinctive reaction, and his supernatural willpower plus resistance to possession should offer some resistance to Danny's possession although Danny still has possession that reaches 4 to 5 layers of potency so I don't know if Ichigo's resistance will hold up long. He also has resurrection so he has some method to get back up. Though looking at the Hollow Physiology, Ichigo's existance/reiryoku is poisonous and erods others who don't have the proper antibodies, depending on the speed, it could potentially overcome Danny's regeneration. Ichigo is also more serious than Danny so this could be capitalized on early in the battle.
Danny has body control on a ridicules level so avoid Ichigo's sword swings won't be a real issue, and while his invisibility and intangibility don't mean jack here, his regeneration, and ecto shields that reflect physical and energy based attacks as well as absorbing the attack if he wants should profide a decent counter to Ichigo's assaults. Danny also has several attacks that ignore durability such as his ice powers which work on people with resistance and freeze them and even pure energy to the point it becomes brittle and falls apart, and his Ghostly Wail which can hit internally and negates regeneration up to Low-Godly, so Ichigo wouldn't be able to recover. Duplication would also give him a minor numbers advantage as well.
Overall, the idea of the match is fun. But sadly, in reality, Ichigo's mere existence destroys Danny if there were no restrictions regardless of Danny's higher tier or speed. Hopefully the new Danny Phantom Graphic Novel provides the ghost boy with something that could make the match doable but that doesn't come out until next year. So with that, I'm done.