User blog comment:B214/Volume 23 discussion blog/@comment-77.188.219.183-20170424155339/@comment-30048084-20170425170017

They will always be equal, how else will the legendary fight of the two Heavenly Dragons continue. The infinite rivalry of the two Heavenly Dragons begins.

also we can already see that Vali will also get a ExE mode. Lilith (his great grandmother) will most probably say that Vali is only able to access a fraction of his Demonic Powers or some other unique ability resulting in his ExE form.

remember Issei is the Dragon God (DxD G) while Vali is the Dragon Lucifer (DxD L) there must always be a balance