I have them both. I have probably hunted with the ACE 250 as much as anyone on the site. I think the Umax will mask iron better than the ACE. The Umax is much simpler to use but is lacking in ability to "identify" your target. Identifying a target is never perfect, but the ACE is better. Depth? I can't tell any difference if you use the ACE in all metal it is just as deep in my experience. If you like icons and LCD readouts, the ACE is for you. Some people don't and then the Umax is your choice. Some people complain about not being able to pinpoint accurately with the ACE but I have never found that to be a problem for me. The Silver Umax has no pinpoint feature and you have to use the old exing method of pinpointing. The ACE has multliple tones and the Umax is pretty much the same tone on all hits. It also lacks a depth indicator that the ACE has. Not necessarily a handicap unless the target is really deep and then it's a guessing game. So, half dozen of one, six of another. I think the ACE is a little more sophisticated and is more readily able to turn on and go. So, I'd say go with which ever one you could get the best deal on. That could include extras like a second coil or a carry bag, etc. Monty