Hi Prospector.
I own both machines. I've got around 500 hours total time on them, with close to an even amount on each. I enjoy them both, but for different reasons.
As far as depth goes, the Ace has an inch more reach than the X-Terra, using standard coils. Our $2
coins hit just like your zinc pennies, even similar in size. This was my test coin in all depth tests. The X-Terra has a maximum reach of 7.5 inches in an air test and the Ace was 8.5 inches. I have previously tested them in dry beach sand with their respective large coils. The same coin had a max depth of 8 inches with the X-Terra and ten inches with the Ace. in wet sand, 5 inches was the max for both detectors. Also, the Ace, with the large coil on, is the same weight as the X-Terra, with it's standard coil on.
The Ace has better ergonomics than the X-Terra, out of the box. I took an angle grinder to the X-Terra to improve things. Also, the Ace kills the X-Terra for what you can do with it's pinpoint mode, also a lot more accurate. The best I've seen. the Ace can also get in a lot closer to play equipment than the X-Terra's. For locking onto targets, the Ace does it better. On a recent hunt with my Explorer, I recovered a few coins via it's audio that the numbers were jumping around a lot like a junk item.They were slightly corroded. When I tested these with the X-Terra, then the Ace, the X-Terra's discrimination jumped around to the point, that I would have left it there. On the Ace, they all gave solid locks and pinpointed properly. They would pinpoint on the X-Terra's.
the X-Terra's to their credit, have a more pleasant to the ear audio system and a VCO that goes some way to telling screw caps apart from coins and has a slight advantage over the Ace for separating Aussie coins from square pull tabs. I Don't like the X-Terra's pinpoint for actual coin recoveries. These days I don't use it's pinpoint mode to actually find the target, I just watch the ground for where it sounds off when the coil passes over it. the X-Terra also has a volume control, the Ace doesn't. I wish it did, as I don't like wearing head phones. The Ace needs to be used with headphones that have a volume control.
The X-Terra's have a slightly faster recovery speed than the Ace, so can be swung a little bit fast; not much though. The Ace's elliptical coil sees less ground than the round X-Terra coil, so can get in between junk more easily. The X-Terra's can handle more moisture than the Ace.
That's about all I can think of at the moment.
Good luck.
Mick Evans.