Jeez, we've been through a dozen different. We're lucky enough to live in the land of diaper friendly water, which helps. I also add Biokleen BacOut and/or Borax to the loads.
We use most often Seventh Generation (which does come in scents, but we don't use it b/c it reacts poorly with the smell of pee imo) and I give it a 10. I use the line for HE, which is only a tiny bit.
I gave up on Ecos when they started adding the softener to all their varieties, before that we used it almost exclusively and I would have given it a 10 especially since it comes in a bigger bottle for less than 7gen. But the softener wrecked my dipes and required serious stripping. So now I'd give it a 0.
I like Ecover, but it's bottles are smaller than 7 gen, so the cost isn't worth it. I'll grade it 9.
We used biokleen for a while, the big cheap box of powder, and it did a good job cleaning, but it's complete & utter lack of a smell was bad especially when line drying in the city. Grade 6.
DH picked up a bottle of ZUM frankinsence & myrrh scent, and it was gross! It ruined the diapers, I had to strip them through the machine like 10 times, and then through the dishwasher like 4 x! The smell made everything disgusting, and it was just awful. -100
I'm sure there have been others, but these are the ones I can recall off the top of my head. We only use natural products, so I can't speak to any of the others.