Alright. From an engineering perspective, and just overall coolness, the original T1 Endo from HT wins hands down. Superb sculpt, each finger has articulated knuckles (4 points), toes are also individually articulated. Just can't beat that level of detail. Only thing is it's not as shiny as some would hope, but in the right lighting condition it still looks great.
The Genisys Endo is set to beat the original in terms of paint, but I'm seeing trade-offs in that the hands and feet are single mold. I suppose that improves durability and stability, but the original's articulation continues to blow my mind even today.