When thinking of any new machine, if you can, test before buying.
Most detectors made today get very similar depth when used in mild soils with the same size and type of coil.
The major issue today is the coil and the circuitry associated with that coil (the receive section).
Some brands/models have cheaper coils and associated circuitries and some expensive brands have very sophisticated advanced coil systems (Nexus for example).
But price doesn't always indicate productive abilities. Don't be mislead by all the hype you read. I've purchased very expensive detectors and found less with them than I did with machines costing 1/12 the price (yes, I'm serious).
When it comes to actual coin/ring detection in mild soils, all detectors today regardless of the price are basically the same (as far as results).
The difficult soils require more sophisticated electronic circuitry (in the receive section) plus the more advanced coil designs.
You can still find stuff with the low cost machines, but at these unique locations (rather rare), you'll gain inches of depth with a more advanced circuitry machine.
No, not all detectors are exactly alike in all soils.
As for the Ace, I haven't used it but I'd guess it to be pretty much inline with other "major brands" ranging from $50-$800 in price (considering cheap Chinese to expensive name brands). Now, this would be in mild soils--not the more challenging soils. Then the story can totally change.
The biggest thing in this hobby isn't material but psychological. If you really believe in your machine you'll find more because you'll work harder.