I have planted both in the ground some years, but watch out: they love it, and they really grow (especially the Brugmansia), and then you have even more of a beast to exhume and repot and drag back inside. I have a friend who cut his Brugmansia back hard to fit it in his greenhouse it got so big! My original cordylines got so big I couldn’t deal with them any more and finally composted them (hate to admit it, but where was I going to store them since I couldn’t get them into the basement anymore?). Funny you should ask this right now, because I was just today looking at my big, overwintered plants from last year (some Phormiums, a big red cordyline, etc.) and thinking about bedding them out instead of trying to come up with an even bigger pot for each. One thing about bedding out big sub-tropicals like this: you only need a storage pot, not something huge AND beautiful like you would for displaying the plant in the season, so you can get by with a giant black shrub or tree pot discarded from a local nursery for your overwintering container.