User blog comment:B214/Question and Answers 6/@comment-207.242.44.6-20190213200838/@comment-37165251-20190214005610

The strongest Charackters seem to be the ones that are good in two types.

See Sirzechs...he is a Ultimate Wizard Type, but he is also incredible Powerful... Or see Ajuka...with his Kankara Formula he is in a sense a Technique or Wizard Type (not sure what Kanka is counting) but like Sirzechs also incredible Powerful.

When it comes to Issei and Vali you can say that Vali is a Power/Wizard Type...Issei is a Power-Type but lacks Magical prowess like Vali...so he will be going into technique (which he showes in his Fights when he starts to think, like against CaoCao)