thinking about moving up from a 1D3 to a 1D4 body ,is there that much difference ,if any between the functionality of the bodies I.e I know you gain 6mp and twin processors but has anyone else made the move previously and seen a improvement in iq . I have ruled out returning to a 1.6 crop camera as I prefer the larger sensor quality ,if there's not enough in it to warrant a change any suggestions as to what next ,I have already owned or used 80D ,7D2 ,and most other canon bodies .i only shoot wildlife and use mainly a sigma 150-600 sport . Recently looked at Panasonic micro four thirds bodies to but I'm sat on the fence with that . The only other option i can think of is a 5d2 that's within my pension budget range ?..??..?