I thought Ryouga and Ban were great, inspiring characters, who each possessed an infectious optimistism and good-heartedness. They were also capable in battle and while they didn't act as their team's strong commander, their spirit rubbed off on them and made them better for having battled alongside them. Kai had less going for him, he was immature and pretty annoying--I wouldn't have liked him if not for the dynamic with his family. However, I ended up liking the entire Ozu family as a whole and Kai worked as the impetuous youngest brother, who leads the charge, but ultimately heeds the command of the eldest, Makito.
Having said that, I thought Satoru was an excellent change of pace. If he was completely stoic and humorless, he would be incredibly boring to watch. Instead, they made him a serious and authoritative leader with an adventurous spirit.