Unless the ninja is specifcally tthat like Ronin Naruto for taijutsu an kakuzu for ninjutsu you should generally get both up with magatama's an sso on. Things like mood help an are generally + for what there growth stat is highest an - for usualy life but again it depends on what your using hem for. Earh main as an exmaple wants resistance for his shields. but you could go life if you wan it to maybe last longer. Most ninja's like Shizuka have a 50% dmg split between tai an nin so it's up to preference.

Where do you see a 70% 50% split? Most of the time ffor mood just look at growth rate. Otherwise if your talking about he paive then yeah it's better to even it ou. Unless they are specifcally tai/nin such as Ronin naruto or kakuzu since there dmg is entirely focused on one side.