Re: 12" is $100 better than a 9.5"
Just speaking in general: The larger the coil, the deeper you can go. But there is a "point of diminishing returns", when it comes to coin-sized objects. That point is usually around 9" to 10"-ish inches, depending on the specific machine. Once you get larger than that, it's only larger objects you'll get deeper, not coin-sized targets. And then there even becomes a point (the hullahoop sized loops?) where you can't even pickup coin-sized objects. By extending out that logic, you can see how some tiny objects (earing studs, little charms, etc..) might be harder to get when a person moves to the very big coils. But once again, that is determinate on the coil, brand, machine, etc.... I've seen how the WOT (15" for the Exp) still seems to get small sub-coin sized targets. But it's fishier and you have to go slower, etc...
And there is inherent drawbacks in larger coils: Fishier pinpointing, poorer target separation, more prone to masking, etc... Of course, if you get a coil too small, (like some brands have 4" and 5" coils) and then you loose depth, but you gain target separation, better averaging (d/t it's "seeing" less soil and less targets per swing/scope). And you can usually run the smaller coils with a bit more sensitivity & bit higher gain, d/t you're "seeing" less minerals in the scope of view.
So as you can see, there's a lot of tradeoffs. If you have a fairly clean area (like the beach where targets are spread out, and you want more ground coverage, larger coils can help. Just keep in mind the inherent drawbacks.
In the case of the 15" Wot, (to use that as an illistration), it does not pick up coin sized targets any deeper on the Exp, IMHO. It just increases the coverage area (with the inherent drawbacks). So I usually stick with the stock 10.5". But I've seen guys do deeper with the Sov/Wot combo though. My experience with Whites (the Eagle SLII in this case) was the same: When I tried their humongous coil (I forget the inches) I found that I did not increase depth on coin-sized targets, and seemed to have to lower the depth, sounds and tones didn't come in as good etc.. Now doubt better if I was searching for soda can and toaster sized objects, but not an improvement for coins. Your MXT, seeing as how 12" isn't a
lot bigger than the 9.5" is going to be a closer call. Maybe someone has specific experience on that combo, and/or maybe you're just going to have to try it. You can always put it on ebay if you don't like it, and maybe break even
