Tough question but a fun one to discuss. I love the Simplex and for the money it absolutely can't be beat. A lot of you are saying AT Pro yet I haven't seen anyone say the Apex yet. the Apex will smoke the At Pro, the problem so many seem to have a problem with it is the ACE name. Its so much more than an ace. I think my choice would be the Apex with the Simplex following closely behind.
Under a thousand... For me its an easy choice. The Rutus Alter 71 for me. In my opinion it outperforms the Deus,ORX. I don't have enough experience on the Equinox to give my opinion on which I think is best but there is one thing that is an absolute deal breaker for me when it comes to the equinox detectors.
COILS!
The lack of coils offered for the equinox series really sets it back in my book. Rutus, much like Nokta/Makro are offering a lot of coils including Concentric coils that are a must for me when relic hunting in moderate soil. In my experience time and time again, different metal detectors, Concentric coils beat out DD coils in the heavy iron.
The Rutus also has a -90 to +90 VDI range OR a 1-125 range, I like that separation. You can also run it mixed mode. True all metal and disc mode simultaneously.
of course this is just all my opinion and preferences for what I do. The great things is we can have a conversation like this because there are so many great metal detectors on the market from some great manufacturers!