Having some experience with Android & ArcGIS development, I can say that pretty much any current Android device will do (performance-wise). However, you should specify minimal screen resolution and internal storage size. And if application needs specific location, users should disable other location services beside GPS (such as cell towers).
If your application relies on hardware buttons (home, back, settings), then devices should have them. Some only have one.
If application needs constant data access, then an unlimited data plan is necessary for outdoor work. If data is loaded onto device before, then minimal storage requirement must be set.