I tested and have been using AGM spotters since their arrival.
The newest Seeker 15-384 is a great low priced unit that takes an 18650 battery, which was the one thing I disliked about their earlier offerings with internal batteries.
It's my current backup/loaner spotter.
I keep the TM15-384 in my varmint van now.
I used it so much that I wore the buttons down and it's still holding a charge after three + years of use.
I gouged the germanium lense of the Fuzion 35-640 and although it has a dead pixel that cannot be repaired, it's still rocking and useable.
For the price AGM is hard to beat.
SJC