H,do you use ext's? what lenses do you use for wildlife? what types of willdlife do you like to make images of? I want to upgrade form the 1Div but have little other real world experience to draw on bar scrubbling about making images of said beasties. I think with these two cameras you have chosen,which I have read about fairly extensively,(BUT NOT USED !!), all these little facets are going to effect what is best for your personal needs.
1dX 5Div are very close and tricky to separate for me personally, i'd be looking at things like the f8 limit on FP's speed of AF, low light performance. Ha ha not having a light up red FP on the 1Dx like i have on my 1Div is a silly stumbling block for me
My humble advice would be try to tailor the new body to what you specifically do as closely as possible. You have made no mention of weight and one series being an issue so,you will have a natural affinity with those bodies if that was your chosen path as a plus.
Mate a couple of real world examples to try and illustrate me thinking

:if you shoot mainly BIF i'd lean towards 1DX if shoot say more static images say genuinely wild deer,the the extra pixels on subject and larger FP array might sway you towards the 5div
I can't really advise you here,bar muse some of the thoughts running through my head, as I'm musing a similar upgrade.............they are simply tools and you need the right tool for you,not me or anyone else. To me grabbing that right tool is down to you analysing your needs
good luck
stu