Well, after seeing the Switch perform for the first year (or less) I think I wager a prediction about the lifetime sales. I say, PS4 will in the end have sold more than Switch.
My reasoning: We have two threads comparing sales from launch in different ways:
Switch and PS4 perform similar. Well PS4 is in front, but PS4 had already an christmas in this statistics. Switch will pull in front soon with with it's first holidays, then PS4 will come back with it's second. But overall momentum lokos pretty similar. So I assume this will hold in the future too.
But PS4 had a weakness in Japan around launch. Sony neglected in the beginning the japanese customers too much, and it showed. But since Sony has worked to remedy this error.Many japanese oriented games were released and recently Dragon Quest and soon Monster Hunter show more effort in this direction.
Switch has a similar weakness in europe. But while Sony remedied the problem for Japan, I think it will be pretty hard to do for Nintendo to pull something similar in europe. I might be wrong, but I don't see much what Nintendo could do. Europe has no specific exclusive that pull much of a platform (it's more about multiplats like FIFA). Exclusives that work in europe usually do that worldwide. And Nintendo had these already, these are selling the system in america and Japan. So I don't know how Nintendo could fix that.
That means, that in the long term the momentum of the PS4 will outdo that of the Switch. Not by much, but enough to be in front. I guess PS4 sells way past 100M while Switch will stop there.
But that is my opinion, what do you think?