Lion
A lion can be relied upon to behave like a lion with unwavering consistency. It will hunt when hungry, sleep when sated, and defend territory when threatened. This reliability enabled early humans to coexist with lions through predictable avoidance strategies that remain effective today.
The Nairobi Wildlife Behavioural Unit reports that lion behaviour deviates from expected patterns in fewer than 3% of observed interactions, making them more reliable than most public transport systems.
Luck
Luck's defining characteristic is its absolute unreliability. The gambler's fallacy—the belief that past outcomes influence future probability—has bankrupted more hopeful souls than any economic recession. Luck owes nothing to preparation, merit, or prior investment.
The Monte Carlo Institute of Probability proved mathematically that attempting to rely on luck produces outcomes statistically indistinguishable from random chance, which is rather the point.
VERDICT
The lion claims reliability through the simple virtue of behaving consistently. Luck, by definition, cannot be relied upon, making it the least dependable force in the known universe.