Which one do you find more dangerous, The T-Virus was responsible for the creation of the majority of Umbrella Bio-Organic Weapons, while The Dark Liquid was a pathogen manufactured by the Engineers for war and genocidal purposes.
As seen in Prometheus, Once exposed to another organism thats been splashed or covered with a heavy amount, the virus begins mutating its host. The host becomes extremely aggressive and seemingly mindless as it attacks any living thing in sight. Geologist Fifield was exposed to the liquid during the expedition of LV-223, mutating his appearance and causing him to attack his fellow crewmembers. He was also extremely resistant to physical injury, being able to withstand multiple gunshots. It took several shotgun blasts and being scorched with a flamethrower to finally kill him, many puddles of Dark Liquid also mutated several worms found in the Engineer ship, turning them into the aggressive Hammerpedes. The Hammerpedes exhibited acidic blood and the ability to regenerate lost body parts. When David used a tiny bit of the Dark Liquid on Holloway it made him very sick and weak.
It appears the larger the amount, it makes the creature or human into a powerful monster.