Compared to an F-2 in Oregon or Washington the Aces (all of them, including the 100, 150, 250, and 350, etc) really suck in our high iron (magnetite) soil here.
Wrapping a metal detector around the nearest tree is not my idea of fun, so people should consider this before buying. I have seen this done, so it is not a joke. In fact, try before you buy is the best motto.
And yes the Aces use some really antiquated circuitry while the F-2 uses more recent circuitry advancements - made within the last 5 or so years. The lower priced Tesoros use a tank circuit that is lightning fast, maybe even faster than the F-2, but not by much. The original cheaper Silver Sabre Tesoros discriminated a bit better than do the modern ones but got approx 1" less depth in average soil.
The Aces have a slow (delayed) audio response and it can be quite annoying to someone who is well-experienced. They are almost a carbon-copy of the original early 80's Bounty Hunter Red Baron and White's 5 and 6, 5000 and 6000 series detectors.
The Silver uMax and the Golden, the Compadre and the Cibola have auto ground balance which works much better than manual GB in our soil (here) in Washington, Oregon, Idaho, California, Nevada, Montana, New Mexico, Colorado, and Utah. Eastward of there the soil is "wussie soil" so the rules all change. The reason it is this way is because of #1 the speed of retune to null, #2 the super-fast tank circuit as a processor, #3 because of it's reduced sensitivity, and #4 because you have to fool with the manual GB every ten seconds due to all our high minerals here..
DO NOT BUY one of Tesoro's high-end detectors for this part of the USA because you will really get P----d off when you don't get the depth of the guy next to you with a lame cheap Korean-made detector (with it's automatic ground-balance).
I would opt for the F-2 or the Silver uMax as a first detector but the Silver is better made and gets 1/2" to 1" deeper in average soils here.. I have owned, do own, or have used all the above detectors in question, plus about 200 others, at work or at play.
LL