Which is more dangerous between a chimpanzee and gorilla....

Chimpanzees are more dangerous than gorillas.
Note: I have not posted pictures of Charla Nash who was attacked by a chimpanzee -- because the pics were too disturbing for me.
(1) This is so, because for most part Gorillas are vegetarian and do not hunt or kill and even in fights among gorillas, the battle is for dominance and not to kill or maim the other.
(2) However, chimpanzees are omnivorous, and enjoy meat and often groups of chimpanzees hunt even other apes and very rarely (but they do) even indulge in cannibalism-- killing and eating other chimpanzees OR snatching infant chimps from females and eating them up.
(3) There is even a sub-specie / culture (it's not yet clear which since further study needs to be done) - called the "Billi Ape" - this is a gorilla-sized chimpanzee that knuckle-walks like a gorilla and is of a size comparable to gorillas-- these "Billi apes" can even hunt lions and leopards-- and such is their dominance and terror that even when billi apes make nests on the ground- lions and leopards run away in fear of them when they howl their eerie howl at night.
Among the first human-billi-ape encounters was one where scientists chanced upon a billi ape feasting upon the flesh of a big-cat (Lion or Leopard) it had killed.
Finally-- chimpanzees are known to rage or turn psychopathic-- including the case of a woman where a pet chimpanzee attacked her and ate up her face-- causing her to go blind and be one of the first recipients of a face transplant.
Therefore, No doubt, chimpanzees are more dangerous than gorillas.
Hope this helps.
Gorillas are not likely to attack a human - and in fact there is no evidence to suggest that a gorilla has ever attacked a human - unless their babies are under threat from poachers. Even then, the intent is to keep the infant safe, not to maul a human. If you ever charged by a gorilla, stand still (as hard as it can be) and do not look the gorilla in the eyes or smile.
Chimpanzees are impulsive and can be unpredictable. They are adorable when they are the size of Curious George but when they reach adolescence - around six or seven - they are no longer cute and fun. They are muscular bundles of raging testosterone and when they attack, they not only are five times the strength of an adult human, but they will also bite with a fierce set of canines that can exert 20-times more force when biting than a human jaw can.
These creatures are capable of cultural sharing and social hierarchy. Oblivious to their own pioneering spirit, Chimpanzees seem to be the smartest mammal on land that is not a human. Gorillas aren’t too far behind, showing great sophistication and probably the most rigid of social organizations amongst any of the primates on earth.
Gorillas have the very rare luck of being able to consume things that others simply wouldn’t eat. Thistles and bitter branches, termites, and ants. They do not eat meat aside from these insects. Chimpanzees on the other hand - will actively hunt and eat bush-babies and tree monkeys.
If you had to be mauled by one or the other, the gorilla is many times stronger but the chimpanzee is much more likely to bite your face, pulling the skin away from your skull while using its feet to gouge your eyes out while the other hands pull away at your hanging body parts. You would be spurting blood from your freshly torn arteries at such a rate you would probably bleed out within several minutes of your initial attack where the severe pain would put you in shock that would quickly lead to your death.