Hi Nigel,
I have used both Samsung Tab Active 2 and 3 with Field Maps. I must say Field Maps worked better with the 2 than the 3. I have had instances of Field Maps crashing while I am collecting lines and polygons. I'm not sure if it's the Tablet or Field Maps, but I've taken to using Avenza for collecting this kind of data. Frustrating. Esri are you listening?
One very odd thing about this (particular?) Tab Active 3 is sometimes these little 3 mm bubbles float around on the screen accompanied by a temporary freeze up of whatever program is active. It's almost as if there is some kind of virus in the Tablet. Not happy about that. Very weird when one has been out in the field all day and it's now 3 pm in the afternoon, this kind of voodoo is going on, and you've still got ground to cover.
As far as the internal GPS goes you get 10-30 ft accuracy. With a Juniper Geode external antenna in the top of your pack you get 1 ft accuracy in the open and 6 ft accuracy in canopy.
A rubber case with a strap to hang around your neck and a glass screen cover are a must. An Otterbox battery backup power supply is also necessary, especially in winter.

Since I'm here in the confessional, has anyone else experienced this with the Tab Active 3?