We have Invisible Fence, but it hasn't proved to be the most reliable in our case. Fortunately we live well off the main road, so if it's down, my dogs aren't in the road. But many of our neighbors have it and are happy.
I think the smaller amount of space you're doing, the better it works. We have over two acres "fenced" and I think that's part of our problem.
Another thing to keep in mind is customer service. Go with the one you think has the best follow-up service. Our particular Invisible Fence office isn't the best to work with. Nice guys, but slow and often don't get back to us.