What the heck are you doing with 3 similar detectors? Gotta have the latest or do you do testing/reviews?
I started metal detecting around five years ago. First bought the White's Spectra V3i. I liked the machine and found many nice objects with it. But my gripe was the lack of weatherproofing. I go out in the rain and snow and around wetlands where I could drop and fry it. Plus, it was kind of clunky and didn't break down nicely into my field pack. The electronics carried the White's legacy but in an outdated chassis.
I bought the Nox 800 and really liked it and it also produced great finds. But it picked up a lot of noise. I spent the money on Steve's fiber rods and bought the Nox power pack. I was interested in the Manticore as soon as it was announced. I laid down the complete cost to get in line to obtain one. But it seemed to me like a bit of a PR stunt. A retailer had my money for several months with no solid ship date. It reminded me of the Microsoft Windows vaperware incidents, waiting for delivery of announced upgrades. I really saw it as a way for Minelab to fend off potential XP buyers, which were available and getting great reviews. I almost purchased one. And I'm sure I would be happy with one.
Instead I got my money back from the Manticore, lost my place in line, and bought the 900. I was certainly happy to get some extra cash back. I liked the 900 and if there was no such unit as the Manticore would be happily using it today. I had all three coils for the 800 and was happy they were transferable. I have found the stock coils to be the best for me. I liked the concept of the large coil and felt it may have fished out some depth and small objects, but swinging that for an 8 hour day was a bit tiring. Especially hiking an hour in and out of sites with a backpack. I jokingly called the 15" the toilet seat.
One of my biggest tests is hunting with the Manticore next to the only big cell tower in my region. It was placed smack dab in the middle of a 1700s farm with cellar pits and small colonial cemetery close by. The 800 was nearly unusable. The 900 was a step up, taming the noise. The Manticore is a vast improvement, the only sacrifice being dropping my sens down to 25 rather than the preferred 28-30. I've noticed the same thing around power trunk and transmission lines. I don't even force cycle the Manticore noise rejection to get it to quiet down next to the tower. Usually I am in the woods so noise is not really an issue. But when I do get near town, I become aware of it.
One of my Minelab gripes is between the 25 and 35 pin pointers. The newer red 35 keeps syncing with my detector and driving me nuts beeping, having to hit the power button to get it to disengage. But this could be the cost of running the detector hot.
I honestly can't go into the weeds discussing the finer points of iron rejection. My colonial sites have such minimal debris fields that I will dig up most solid hits. Yes, I look at some big iron, but I often find it interesting. I will sometimes collect a long beautiful hand forged spike and I photograph all of horseshoes to document styles and ages. I like seeing iron pot shards. Seeing nails lets me identify age ranges, and frequency lets me know if a structure was there. Nails were a form of colonial currency. I'm not picking through nail beds. I'm convinced the colonials reused the nails or melted them back down.
The Manticore has produced small silver at 6-8" depth including trimes, reales, dimes, and half dimes. Solid tones at depth. It has identified finds from sites that I previously hit hard wit the 800 & 900. But in all fairness, we know how that works. You can hit a site at different pass directions and weather conditions or luck and keep pulling things up. Can't just credit the machine. I will say that of all of the large cents, draped and liberty heads, and even Indian heads, I pretty much know what it is before I dig. The size and shape of the coin on the right center line, as advertised. The only thing wasting my time are pre-1960 shotgun shell bases. The paper rots off and are a perfect round brass disc. But I can't notch out that range without losing something good.
I do like the technological side of detecting equipment and want to experiment. But I don't believe in collecting machines as they quickly become closet relics. I gave the 800 to a youngster who didn't have money and was excited by the hobby. I sold the 900 at at third of my cost and it was in mint condition. The way I look at it, my time is precious. When I go out detecting I want the best machine that I can afford in my hands to best increase my chances of finding what I am after. Yes, I would buy a Manticore upgrade tomorrow if it were available.