riot you said dot are toxic cause you don't know how much damage you would receive

you can tell how much damage you will recieve tho..

One difference I can think of is that it's DoT caused by you, so you are expected to know exactly how it works.

There are ~130 champions, most people would not know how much DoT opponent's ability causes, it is unreasonable to expect otherwise. But if the source is your own item, yeah, you should be able to tell after a game or two with it.

So imho the less DoT the better. Except for Teemo, because Teemo's identity is the frustrating toxic champion to play against :P.