Hard to say, I feel the same about both of them

I don't think yellow and pink go well together, but with all that white it looks better, so Stress really seems to know how to make difficult colours work together.
Though the skin colour doesn't suit the pink or the yellow.

As for Pweep, I quite like the combination of blue and brown, they do work in many circumstances yet we don't see them together often enough.
However the pink fluffs on the ankles look a bit off, and there are one, maybe two too many objects on the head.

Overall, today I'll saw Stress is the avatar I favor. If only because the bright colours cheer me up.