all he had was spirit gun. -.- but w/e. I'll just add, if you have spiritual energy in you, and aren't aware of it, doesn't mean you're not using. E.G. KUWABARA and ICHIGO being able to see ghosts/spirits and such. They didn't know wtf or how the hell they're doing it, it just IS. So naturally you can assume that the innate ability of the Mazoku and such was just a normal thing for Yusuke, he just wasn't aware of that factor. So the only thing spiritually brought to his attention was the fact of how to use Spirit Gun and channel it. As far as being able to see and react do Hiei's speed, that could of been is normal eye reaction time. See, he was able to keep up with 'normal' Hiei speed. Which was impressive, and impressive Yusuke could react. But once Hiei stepped those bounds of a human based vessel and used the Jagan eye to go into demon form, Yusuke wasn't able to keep up then. And yes, he had to beat Gouki by shooting that spirit gun down his mouth. He had to beat Hiei by reflecting the spirit gun off the mirror of forlorn hope. But that's all he really had. Was that spirit gun. Any way....besides the point
Normal fighting. Street Fighting. That is what Yusuke does, day in, day out. He's an ass hole. He fights dirty. This is where he excels. bigger doesn't mean better. Not here. Kuwabara can take Ichigo, and then its Chad against 2. Yusuke is respectfully more nimble then Chad, who is good at tanking hits but, wtf is that going to do him if they gouge his eyes or Jab his temple.
Chad is strong but he's a loyal, honorable guy. Respectful. Yusuke sure as hell aint like that, (Kuwabara is more or less though) I know that on a physical endurance and strength level, yeah, Chad is a pretty above average human. But where it counts to be an ass hole and fight like a prick, using your brain, I just don't see him excelling like Yusuke or Kuwabara would.
sorry, I don't know much about Getbackers. I'll have to read about them.