IMO, the biggest con of a spotter is eye strain if you're actually scanning with it. I use mine only when I have found something in my binos that I want a better look at.
Concentrating through one eye, while moving the scope around gets old real fast. If you're actually looking for critters over fairly big areas, big binos are the way to go.
When in the forests of western Montana, which is closer to the habitat type that I suspect you're talking about, I rarely look at something at more than 5-600 yards away. I usually don't even bother with a spotter there if I am just after deer or elk and don't need to get a real good look to determine legality. I just carry my binos.
