Which is less toxic to humans, saliva or urine?

Toxic to the environment? Toxic to the body? Depends on the concentration, content and the quantity.

^^^^Edited.

Saliva. Unless it is the saliva of the Gila Monster. You did mean human saliva vs human urine? But survivors of sea disasters (like the USS Indianapolis) drank their own water.

Oh big wow! I changed “volume” to “quantity”. HA!

Up until 2014, urine was always said to be sterile, barring any UTI the donor may have. Subsequent work done at Loyola University has supposedly proven otherwise and this has caused the medical schools to modify what they teach.

The human mouth is full of germs as is it’s product, saliva.

If I had to make a choice, I’d still go with urine.

I figure, under normal circumstances they must be equally not toxic.
I am sure I am exposed to both when engaging in kissing or oral sex with GF.
Have not gotten sick yet.

Yep, I’d go with Urine too. I had always heard the same thing as what @Espiritus_Corvus says, that Urine is a sterile fluid unless their is an infection in the bladder or urethra. Guess not, but better than swapping spit. haha
We are treating a goose right now for Avian Chlamydia and it is a potential zoonotic disease, so no swapping body fluids with the big gray lady. haha