Switch will win in the US, probably lifetime. It'll obviously win in Japan too, it's the European sales that are going to let it down and hold it back from winning globally.
Switch shouldn't have a problem to have a long tail. It's Nintendo's only console now, so Nintendo's top development teams don't spread their attention between two consoles anymore. More high profile games, more sales.
Plus Switch sold so well that it made past the two-year-mark without price drop or revision. This leaves all the options to reinvigorate sales for a long period of time. The European market is historically more price-sensitive, so Switch can gain ground on the PS4 over time. Globally, Switch will come out on top in lifetime sales because the small deficits in Europe and the rest of the world aren't going to offset the clear wins in Japan and North America.