@rein: Nappa and Raditz are strong, but that's all they've got going for them. Raditz is at average intelligence at best, and Nappa's pretty thick. Akatsuki and Gotei 13 have both brains and brawns behind them. Hell, Itachi alone could make short work of Nappa.
It's not a question of strength. Nappa and Raditz are strong, but put them against guys who create illusions, warp reality, create black holes, burn stuff forever by blinking, summon sharks, freeze stuff, make you bleed by shouting colours, make you bleed by shouting, make you die by pointing their knife at you...
The Naruto and Bleach team just have FAR too many tricks up their sleeves to lose this one.
@SamJaz: Both raditz and nappa are at a point that a guy who can destroy the moon feels he's worthless against them. None of these characters are above city tanking durability, with a wave of their hands this group will be dead.
@rein: They have electrics going through their brains. And if that doesn't work, Ameteratsu.
Also, worth pointing out that Ichigo's at city levelling power without the hollow mask now, so there's one person who can take the Saiyans on in equal strength in case the other tricks don't work. Which reminds me. Sasori poisons people. Hidan makes people die by licking their blood. Madara can't be punched, and can shove you in a black hole. Gin shoves acid into people. Hitsuguya freezes stuff. Kenpachi's Kenpachi. Aizen's Aizen. Yamamoto's Yamamoto.
It's brains Vs Brawn, and we all know how that works out in Naruto. Bleach and DBZ, however...
Nappa and Radditz have moon plus power and durability. It is likely they have lightspeed reaction time and movements. Ki is spiritual energy / life force, if bleach physics apply then Nappa can spirit pressure crush the whole bleach verse.