Our main pasture is hotwire on two sides, and 5 strand the rest of the way. The hotwire is charged by a plug-in charger behind the house.
We set up a small pasture for mares about to foal or horses that are sick or injured. The first time we set it up, we used the electric tape. It does sag if your posts are too far apart, but if you are in a high-wind situation, it will also stretch. (I live in south-central Kansas, and some days it's still while others the wind blows 40 mph.) The second time, we used the electric rope. I didn't notice the stretching with the rope. Both types were easily visible to the horses. The only thing to keep in mind is if the fence breaks (tape or rope), there might be some fraying. So make sure that there is wire touching wire when you fix it.
We used a Zareba solar charger, but it didn't work very well for us. We have a lot of trees, so it didn't hold as much charge in summer as it could have, and in winter, same problem. To fix that issue, we got a battery powered charger, and that worked very well. I had a gelding who loved to test fence, but after getting zapped twice, he decided that might not be the best idea he ever had.
Learning never stops