What did it say the difference was with doing it all in one?
Can't find the article again but it was trying to hint that you are using a lot of power over and over again, similar to running fast. Where as doing heavier weight is obviously using a lot of power the sort of power you wouldn't use very often. So by doing like I did and did 50 with slightly less weight you're using a lot of power and the muscles are working over and over again with that high load of power.
Only done it once as a test and it was effort, not sure if it's benefitted my legs or if it just wore them out though really