My wife, our twelve year old son, and I were torn between whether we should do Selvatura or the Original Canopy Tour. We had read great reviews of both, and I'm sure they are both great experiences. On our second night in Santa Elena we talked with a family we had met the night before, and they had spent the morning at Selvatura. They loved it, but said that it was very crowded. Despite the crowds, they said it was a great experience and they didn't have to wait in line much. But after hearing that we decided that we'd try The Original Canopy Tour.
We did the 10:30 am zipline tour and drove up there from our hotel (they would have picked us up if we wanted, but it was close by). We were the only ones there and had a wonderful tour with just the three of us and our two guides. Nobody in front of us or behind us. Our guides were wonderful and were not in a hurry to move us along. They took time to tell us about plants, trees and animals. We saw some birds, but no monkeys or anything -- I think it's rare to see them on any of the ziplines in this area. The guide who went in front of us took our camera for most of the tour and took great photos and videos of us.
The Tarzan swing was a fun bonus -- it seems scary before you start, but it was really fun, even for my wife who's scared of heights. Midway through the ziplines (14 cables total, I think?) you have an option of rapelling down and climbing back up through the center of a strangler fig tree. That was really cool, and my son and I both loved it, but my wife opted out of that -- it's probably good she did, because I don't think she would have enjoyed the rope-ladder climb back up.
We were glad we picked The Original Canopy Tour because of the quiet, private tour, but I'm sure we would have had fun at Selvatura, too.