Im the one who started the confusion, I suppose,. Where I find the faster sweep speed beneficial is in areas like playgrounds. There is lots of trash, with some goodies mixed in...plus lots of ground to cover. I should have been more specific.
What it will do is overlook some of the "fiddly bits" like foilies, yet still respond to good targets clearly. Once you find such targets, you slow down to process them. And Im not talking smoking fast speed here - you still have to maintain coil control. Just 10-15% faster.
I have pulled deep coins from right in the middle of the trash by doing just such things. I get a belltone in and around known trash and THEN I slow down somewhat, moving from different angles to focus the field and pick them out among the other targets. I was quite surprised the first time it happened.
But dont slow to a crawl. These Garretts need motion to do their job. In the end it's varying degrees of a "happy medium." Sorry if I caused any confusion.