You should first define your usage scenario. Entry and mid-level VLF detectors are usually sufficient for hobby searches, while Pulse Induction (PI) and underground imaging systems are recommended for deep targets and larger masses.
As a starting point:
- Beach / park / garden → lightweight VLF models focused on coin and ring detection
- Field / land → models with mineralized ground compatibility and adjustable ground balance
- Professional use → multi-frequency devices with advanced discrimination and deep search capabilities