Just watched this yesterday on Netflix as well. After re-watching some of the key scenes, I think he left with real-Sophie for a few reasons.

I think it's more likely the real-Sophie left with him. If you watch the end, it actually looks like he may have left with
real-Sophie (they never tell you for sure except to hint with the bacon
thing). When both Sophies come out the door after fake-Ethan hits the
"wall", real-Sophie is far to the left and asks…

If you watch the end, it actually looks like he may have left with real-Sophie (they never tell you for sure except to hint with the bacon thing). When both Sophies come out the door after fake-Ethan hits the "wall", real-Sophie is far to the left and asks "What happens if we can't catch him?" Fake-Sophie, far to…

I liked the sci-fi angle, but they left so much unanswered and it felt like the first 2/3rds didn't really come together with the last. Why are the therapists (there were 3 pictured) set people up for this? Why does pitting a couple against each other make them stay stuck in the house? Who are the dopplegangers…