User blog comment:Crimson and Darkness/Volume 24 discussion blog/@comment-95.90.224.203-20171105084734/@comment-29963364-20171107023140

While Sun Wukong was training Issei and Vali, he stated how they compare to each other.

Issei out-classes Vali in "direct speed" (getting from point-A to point-B) and power, while Vali surpasses Issei in "being well-rounded" and has greater manueverability (can zig-zag, dash & turn, loop-d-loop, etc.).

Basically, Issei has the advantage in CQC, but Vali has it in Mid/Long-Range Combat.