i know some one who was bitten by a juve goliath and said it hurt like hell, when i say juve it was the size of an adult red knee, so i guess sub adult is better.
My friend was bitten by his red rump when we were younger and he didnt go on about ti too much so i guess it depends on the species.
i would think its more of a shock than anything. ive had a chilie rose scrapping her fangs repeatedly across my hand, very un-nerving but she didnt actually bite. been stung by an emp scorp tho and that just numbed my finger for bout a day