Another thing that would differ Bowser and King K. Rool should the latter be the villain of the DK film.
Basically while Bowser slowly goes through growth as the mario series went on and becoming things like a loving father, a genuine care and worry for peach, and some sort of twisted respect/almost friendship with Mario K. Rool never does. In fact IIRC he actually gets the opposite and each Donkey Kong Country game had K Rool acting actively more deranged and unhinged ultimately becoming downright genocidal towards the Kongs.
You could also argue that Bowser's more of a genuinely great leader and figure among his armies and is able to rally numerous other races and species to his banner where as K Rool IIRC treated the Kremlings very poorly and many where miserable under his rule.
You know it'd actually be ironic if K Rool does appear as an antagonist but when he confronts Bowser a large portion of his forces desert to join the Koopa King instead.
Gonna be a wild day on this thread if the villian is Lord Fredrick instead of K. Rool
Or the Tikis.