It totally varies...But, it should have significant impact. I just had the same collections account on all my reports. I've checked 2 of my scores. I haven't checked TransUnion yet though. Equifax, my score jumped 19 points. On Experian, it went up 39 points. This was just for a $78 utility bill that I never knew I had until I saw it on my report.
With Equifax, that was the last of my negative items. Experian, I still have one left on there. I'm not sure if that has to do with why the changes were so different between the two or not.
Hope that helps!