I grabbed enough netting to enclose about 1600 sq ft last fall. The energizer I have is the pulse-type. It generates in excess of 10k volts. I keep my birds inside the perimeter and move the fence every 30 days or so. (I have 25 chickens, 4 turkeys at present). The fence seems effective at keeping my dogs out. They are fairly large dogs, about 80lbs each. In fact the dogs after a zap or two won't even cross the driveway near the fence. The birds on the inside rarely if ever get zapped. They are happy with their forage space. The fence is 42" tall. They could clear it easily if they were of a mind to, but seem most content within the confines of the fence. I've had birds go over the fence twice. When the wind blew shut the coop door and evening approached, 3 of my chickens jumped the fence to try to find another way in to roost. Introducing 2 new turkeys to the flock last week, the new birds jumped the fence to hang out with their new flock rather than wait for me to introduce them.
Personal impression of the zap: When I'm wearing rubber-soled boots, the zap is clear but mild. In thin-soled shoes, the zap will cause my arm to jerk mildly at the elbow. If I kneel in a puddle and touch the fence, the entire side affected side of my body is thrown a bit. (I don't recommend this latter test, it was a surprise and a bit of a revelation to me).
I've only this one set of experiences, so cannot compare it to the always on. I use a solar energizer and it has been doing remarkably well as far as I can tell. The primary predator I'm concerned with is dog. My dogs respect the fence well.