Daniel,
I have used the following and own them:
Whites
Garrett
HeadHunter
Fisher
The Whites can be ify, The Garrett always there for me, takes beating I also use an Infinium outside of Harbours and the Seahunter in with pulse, Head hunter was great but prone to flooding it needs a more robust headset, but works great on land if only I could trust it underwater, Fisher pings anything, too many techniques,
for field work though the battery life of the Garret is awesome and the unit is good. I treat them all well but they do get bumped dropped or with the owner bounced over the surf zone, I go garret for money and results.
Good Luck 99*