People forget what they read so soon..that amaterasu got nagato because he thought itachi was going to attack naruto..he didn't know itachi has escaped edo tensei's grip..now for the topic..there is a reason deva was used in akatsuki meetings.the guy(though a not actually living) was boss!.a quick massive shinrai tensei(the one that broke boss toad's bones) would fling all the akatsuki members meters away if a mutiny was initiated..and the likes of deidara and itachi who are not tanks will feel the brunt of it with shattered bones..now we know genjutsu aint gonna work on deva,the guy feels no pain.animal path said "I feel no pain"(when it was restricted with a pain induced genjutsu by ibiki and his anbus..now will a living itachi start of with susanoo? That will be suicide because deva will outlast him if he does that..its funny that if itachi tries a close commbat taijutsu and gets hit with a well timed shinrai tensei like the one on the toads,he is done for,as simple as that..
1.Taijutsu-deva went toe to toe with 6tails kyubi and said"is that all you got?" Beat that..
2.Speed-both are equally fast..deva OUTRAN a 6tailed kyubi..that's some crazy speed feat.
3.Genjutsu-unless its tayuya's flute or frogsong which paralyses your body(not psyche because deva is just a re-animated corpse)..itachi won't get him in one
4.Ninjutsu-amaterasu can be sensed and countered with shinrai tensei or even earth technique(deva used it against kyubi's katon)..itachi's susanoo is OP agreed,but can it withstand CT? Remember that even 6tailed kyubi's fireballs couldn't stop the orb alone..and deva could even make a bigger CT(it was stated by nagat himself)..totsuka sword pierces whoever it stabs and puts his soul into a dreamlike world..deva has no soul..its a walking corpse...deva path pound for pound outpowers itachi,truth be told..