Smooth walls in this house, so paint every time. Our previous house had walls that were far from smooth, with plenty of nail holes (I imagine from many previous owners putting up pictures) so wallpaper was the answer - it covered many flaws.
Although wallpaper looks lovely, it means lots of work scraping it off to replace it (which I’m no fan of doing); plus, repeated scraping can damage the plaster on the walls if you’re not careful scraping off the paper.
I’m all for ease when it comes to decorating, and for me, painting is far easier than wallpapering.