Ron, in terms of left/right separation I feel so far the 12x10 is as sharp as it gets, compared to all other coils, big or tiny,concentric or DD, to separate targets from each other. I'm very confident using it in the heaviest of trash.
All about angles, so that the length of the DD line misses forward or aft trash, because, despite what has been implied about VLF technology on certain models, there is simply no way a detection field can see past the first thing it hits, and relate dual target IDs to those two "as one" objects. First (meaning shallowest) object the field hits, and it's game over.
But, yea...In terms of length wise separation, the 7.25" Tornado has already shown me unmasking ability length wise that any larger coil just isn't going to get around, unless you grid from just the right angle(s) to miss all surrounding ring of targets with the DD line to hit that coin and that coin alone. That is where this little coil comes into play for me.
I have owned one other small trash coil, which was a good bit smaller than the 8" Tornado, but even though it's length wise separation was outstanding, I found it's left/right separation *appeared* to me not nearly as good as ANY coil I compared it to, big OR small, so I sold it off and bought an 8" Tornado.
I can live with the 8" Tornado not having better left/right separation than the 12x10, because no coil I ever owned, concentric or DD, regardless of size, comes even close and I can't imagine how it could get better, but that said the 8" Tornado has really good left/right separation, and that combined with it's sub 8 or 9" typical size for trash coils on most machines, means that alone will have it finding stuff other machines or coils can't.
And, combine that with it's apparent super deep abilities for such a tiny coil, and I see a bright future for this coil in the right situations at "dead" sites. The 12x10 may be able to sift out left/right wise better IMO (initial impressions here of course with the 8" Tornado), but it'll take far few odd grid angles for the 8" Tornado to work it's magic...