I selected the He8 for their reliability and needed a large space with as small a number of drives as possible, plus I got the 8TB drives for only $441 each. Enterprise quality (10E15, 2.5M hours MTBF) 8TB drives are not terribly common AFAIK and I have had excellent results with HGST enterprise drives since they first came out. I don't feel comforatable with the Seagate SMR 8TB drives yet, so they were not considered at all, and most of the Seagate offerings are only 10E14 drives with MTBF around 1M hours. The energy savings of the He8 will just be a bonus since they will run 24/7.
So far I am very happy with the drives, and the Adaptec 8805 that I went with instead of the 71605 since i got it for over $250 less and really didn't need 16 ports. I'll give an update report in 3 or 4 months after the data migration is complete and the new array has had some service time.