The best metal detector for hiking should be lightweight and foldable or easy to disassemble so that it fits inside the backpack. I think the bounty hunter 4 is the best affordable option. The lightweight is important so that you do not get tired when swinging a heavy detector for many miles.
Why the bounty hunter 4 is the best?
If you are going for a hike, not for treasure hunting, the bounty hunter is the best affordable option.