For grins, you oughta slap that coil on your 250 just to see how it does.
I'm still betting that the coil is probably 85% of any increase in overall performance,
and that the 250 with that coil would do just about as well as long as the slight
frequency mismatch does not stunt the performance. But it appears not to, being
as they are selling the other older coils for use with the newer 350.
Would make for an interesting comparison anyway..
One thing that kind of makes me think that, is the video's of the 350 air testing seem
no better than the 250 air tests with the 9x12 coil.
Actually, the 250 with the 9x12 seems to beat some of his tests on certain materials.
But I could expect that being as the 9x12 is slightly larger than the DD they are using.
As far as the actual detection, the only difference between the two that I can see is
the slightly different frequency. And I don't think that small difference is going to make
too noticeable an increase in performance, except for maybe a small bit on gold nuggets,
etc. Garrett themselves state that the main reason for the change was for increased
performance detecting small objects. But.. the 250 already was good at detecting
small objects, even with the 9x12 coil.
Anyway, the point is not to slam the 350, which I'm sure is a great machine.
If I were starting out now, I'd quite likely get it over the 250 just to have the
better coil.
I'm just guessing you could get most of the same characteristics using that DD on a 250.
I might consider that coil to further round out my collection for the 250..

But from what I can see so far, I know I won't be upgrading the 250 to a 350..
Just not enough extra bang over the 250 to spend the extra 300 bucks on.
But that's just me.. I'm tight as a drum..
If I upgrade later, the AT Pro would definitely be in the running.

It's got enough extra bang to be worth the extra bucks I think. I like the ground
balance options, and also the digital ID is kind of handy for "fine" ID resolution.
And it has the DD coil.. And 15 khz.. Which is an increase large enough to
be fairly noticeable.
I think they have a hit on their hands with the AT Pro.. If it pans out to be as
good as the initial hype, it could well be their next "Ace 250" as far as sales,
except for mid range, instead of beginner level.
And I'm sure the Ace 350 will sell well too.