Joel,
A couple examples for you....With my 6x8 SEF last year, I located a 1909 wheatie and a 1854 Canadian Large cent in the middle of a soccer field the wheatie was about 8" down and the Large cent was about 11" down(obviously this was a larger target too.)...but I love mine. I recently purchased the 13" ultimate coil. I get great separation and more coverage. Either in my opinion will work just fine for separating close targets.
I'm not sure how to explain which one is better but here are some facts. I have "POUNDED" my yard of this 1800's home I own. Since purchasing the 13" ultimate I have found numerous other coins that the former 6x8 missed in my yard. Like I say..it must've not been able to locate them because I've covered my yard pretty thoroughly. I've found about 10 wheaties, a buffalo nickel and probably one of my best finds to-date. a 2 cent piece 1856 that looks as if it was dropped the year it was minted. What a gorgeous coin. I've yet to post the pictures, but plan on doing so soon.
And I know there are more coins in my yard. I keep looking especially after locating the 2c piece dead center in the middle of the grass...right in the middle of the yard. No spot is ever hunted out. I'm sure my yard still isn't either....I keep trying different settings and coils to search it.
Good luck Joel.
Bob