to shop for a Tesoro that will best fit the conditions you will search and furnish you the best in the way of performance.
You stated: "Depth is not a critical factor in making my decision but have threshold adjustability and a few other features would be nice."
So I believe you have the right idea, and want/need:
Threshold adjustability;
a Threshold-based All Metal search mode to complement Discrimination;
and manual Ground Balance to best adjust the detector for the conditions you will encounter.
There is no perfect detector and some like the Vaquero, while others would pick a Téjon, from the current offerings. Personally, I'd either select an Outlaw, or shop for a discontinued Tesoro that still offers ample adjustment function, such as the Bandido II µMAX or the Eldorado µMAX. If I were picking just one model to hunt farm fields, and I wanted to hunt for anything and everything there, ferrous and non-ferrous, my personal pick would be the Eldorado µMAX, but those are hard to find. I am still looking for a pristine specimen for my own detector battery.
If you want ample Discrimination to reject most common iron, then my personal pick is the Bandido II µMAX [size=small](I have one)[/size] but an Outlaw would also be on my radar [size=small](I am also looking for a new Outlaw with 8" and 5¾" Concentric coils)[/size], and from enough experience hunting plowed fields, open grazing and farm land, and wooded areas, I have found them to work just fine. My primary reason for grabbing a Tesoro is when I encounter severe dense iron trash conditions as they are the models I compare all other detectors against in this challenge.
You're correct that 'depth' isn't always the factor, but with the right coil and search mode set-up, you will do okay with the models suggested. I'd take any of these more versatile models to those with a factory preset Ground Balance.
Monte