Sloth
The sloth is magnificently predictable. Researchers at the Monteverde Sloth Observation Station can forecast a sloth's position with 94% accuracy simply by checking where it was three hours ago. Their weekly schedule consists of: sleeping (15-20 hours), moving imperceptibly (2-3 hours), and contemplating existence (remainder).
A 2019 study in the Journal of Extremely Slow-Motion Wildlife tracked 47 sloths over eighteen months and found that not a single one did anything surprising. 'It was simultaneously the most boring and most reassuring research of my career,' noted lead author Dr. Patricia Slowly.
Chaos
Chaos is, by definition, the antithesis of predictability. The Stockholm Institute for Disorder Studies spent fifteen years attempting to predict chaotic systems and succeeded only in proving that such attempts are 'fundamentally absurd.' Their final report consisted of a single page containing the word 'No' in 72-point font.
From weather patterns to stock markets to why your toast always lands butter-side down, chaos operates on principles that actively resist human comprehension. Even chaos theorists admit they are merely 'chaos observers' at best.
VERDICT
In a rare victory for Team Sloth, predictability goes to the creature you could set your watch by—if you had a watch that only needed to be accurate within several hours. The sloth offers the comfort of certainty in an uncertain universe. You will always know where a sloth is: exactly where you left it.