[addicted2sp33d]

Personally, I would be concerned with either one around me. Both have their dangers.

Sharks are more instinctual killers that might attack because they think I'm a meal.
However, Orcas are far more-intelligent animals and will sometimes just mess with you for fun. They won't think you're food, but Orcas are known to kill whales/sharks for fun.

Orcas get waaay bigger than most sharks in the neighborhood, and when you see one, you know there are more around.

I go by "Land Rules". Just like people on land, most are nice and friendly, but if you run into a 25-foot 10-ton bully who just wants to mess with you, your day can go bad very quickly and there won't be much that you can do about it.

Either way, I would probably have my VHF in-hand if they were consistently within 50 yards of me... and if I see a pod I would at least broadcast an "FYI", if only to let the Orca fans know there's a pod in the area.