I personally like thick concentrated bleach as it works faster, but I do have thin bleach for tasks that have to be done more frequently. I noticed the difference when bleaching the bathroom and how much less work it is. Thin bleach is great for drainpipes to keep things moving and basic cleaning, but using more of it for heavy duty tasks doesn't work.
I like both, but I've never really noticed a difference in the way they clean, they both seem to do the same quality job. I like the thicker bleach because it doesn't splash as much, but that's the only reason.
