Saw this too late to comment. I got cheap bags and they fucking suck. like pop said, one of them disintegrated in water. Desn't matter what the screen size is, if the bag itself is letting water through. Not to mention having peices of bubble bag in my hash.
As for the numbers I ran my 250, 180, 45. Can't actually tell much difference visuallly between the 180 and 45, only that there is less of it. After 2 runs through those bags i ran it once through the 15. I can't say it was a waste yet, but i think it was a waste of time running the 15. Took about 35 minutes for the water to run through, and i was left with a tiny bit of sludge. Dried up over night, but shit better be really good compared to the others. My forearms are still tired.
And i would suggest 3 or 5 gallon bags, 1 gallon are tiny.