Not sure which coil you are referring to. The largest Ace coil that Garrett sells is the 9x12 coil
Now, some third party companies do make larger coils, but I'm not sure if that's what you
mean or not.
If you need another machine, I'd go with a 2nd Ace 250 if you don't want to spend too
much on a 2nd unit. You know what to expect from it.
Myself, I think getting the larger coils can be a good way to increase the depth
and pay less than you would for a higher cost machine.
But.. I've never seen any real decent reports on the newer third party coils.
No comparisons to the Garrett 9x12 for instance. I noticed the price of the
third party coil I saw from one company was quite expensive. A good bit more
than the Garrett 9x12. While it might be pretty good, I haven't seen any reports
good enough to say if it's worth the extra money vs the 9x12 or not.
"Saying it "works great" doesn't tell me much.. "

I want to see detailed comparisons to the 9x12 before I plunk down
that big cash for a third party coil.
So until I do, I can't really recommend it too strongly when you can get the 9x12
for a good bit less money. The 9x12 is still a good bit larger than the stock coil
which is 6.5x9 or something like that. And it will give you a good two more inches
over the stock coil on coin sized objects.
Myself I have all three coils, and find them all handy. They make the machine a good
bit more versatile, and will extend it's useful lifespan before you might consider a
better machine. And even with all three coils, I think it's still less money than the
next grade up in machine which is the 1350, or whatever is next up the ladder.
Anyway, I vote for a 2nd Ace 250, and a two thumbs up to extra coils as needed.
BTW, the sniper coil is great. I actually usually recommend it as the first add on
coil, unless you know you are going for large open spaces and need a big coil.
You might not cover a large area at a time, but the sniper on the 250 is deadly
in busy areas, and still goes fairly deep. Easy 5 inches, and some report a
bit more. I'll say 5 inches just to keep it conservative. I don't like to over hype
specs..
Ditto on the 9x12 vs the stock coil I've actually seen 2-3 inches deeper on the
9x12, but I'll say a sure 2 inches just to keep it conservative so one doesn't
buy one and not get what they expect going by my jibber jabber.
BTW.. I'd avoid the Ace 150 unless dirt cheap. I think the pinpoint mode
on the Ace 250 is worth the extra money. The Ace 150 is not a bad machine,
but not having a pinpoint/non motion mode would drive me batty. Not precise
enough for my tastes. Also the pinpoint mode can be used as an optional
detect mode.
Well, there ya go. My usual $129.39 worth..
