I've used all 3 & still have the AT Pro. The Fisher F70 gave off so many noises when I turned it up, & the ID at depth bounced alot. I dug what I thought were probable coin targets. I knew that the ID still bounced through several categories and confidence meter was low on fairly deep coins & deepest I got was a penny at 5.25" & dime at 5".
The MXT is heavier. The MXT ID is usually good here to about 4" on dimes or 5" on quarters. Had a couple of dimes at 6" & 7" on a couple quarters. Used relic mode, items below disc setting low tone & above disc setting high tone. Rather noisy with sens turned up, but when turned below plus range, less noisy, but volume dropped. In coins mode, rejected items weren't silent, hardly broken up with high sensitivity.
AT Pro, at first, no deep coins & I'm disgusted. Then I started using manual ground balance. What a difference! Used super simple standard mode, coins progam, iron totally rejected (40) & sensitivity 7 out of 8.
Very quiet & stable, then a loud beep. A quarter at 4" or so, very tilted. Then another loud beep, high tone every sweep, IDs #80-85 (the dime range) & depth indicator (even #s only, showing 8).
So I dig down 7" in hard, dry, somewhat mineralized dirt & there is a clad dime. Very "smart" detector to ID a dime correctly at that depth. So it has the record for deepest correct ID on dime in my soil. Just tried detectors under $1,000, but even some with expensive Minelabs say the visual ID is bad beyond 7". The dime was found in a park detected 100s of times & probably sat there 20-30+ years.
Most detectors I've tried have good ID to 4"-5" if that & some say why have visual ID when it lies? I used to agree with that. Dig only probable coin targets & get mostly shallow clad. Or dig much trash to get deeper beeps that could be coins. But now, a detector that IDs properly down to 7"+ makes it possible to get more older coins while digging little trash.
So for best ID at depth, simplicity, reasonable weight & quietness, it is my all time favorite. Plus, it can go in water up to 10' deep. Waist deep water is where many rings slip off fingers & not many pulltabs there. I don't want to mislead anyone, so keep in mind this is in my soil.
The AT Pro favors low conductors. Air test std mode 10" dime, 11" 25c, nickel 12", detects most gold besides flakes, if you accept all above iron.
In unmineralized Florida white beach sand, many detectors will do great.
In hard, mineralized dirt, a few will beat most. Best wishes, George (MN)