May be I haven't make it clear enough.
AFAIK, ECC isn't mainly about "how much difference it make in daily use / specific task", but more on "the data integrity is guarantee".
No matter use ECC or non ECC RAM, any task "should be" finished flawlessly. However, ECC RAM simply allow the user to make sure the result is valid.
e.g. for a 100hours scientific computation. No matter a computer with ECC or non ECC RAM, both of them should give out the same answer (so, ECC or not should makes no difference on this specific task). But on the non ECC computer, the user has no way to make sure the answer is really valid. Even though ECC RAM isn't 100% bullet proof, but we know, in real world, we can assume there is zero undetected memory error on the ECC enabled computer.
Also, when the computer crash etc. ECC RAM allow the user to know if the problem is coming from the RAM straight away. On the other hand, the non ECC RAM computer user need to guess if there is any hidden memory error.
So, the difference is mainly data integrity / reliability, but not ECC can make any difference on any real world task.