White ornaments look great for about ten minutes, then the tree lights come on and half of them vanish into the branches like they never existed. That's the warning. If your tree is heavy on warm white lights and pale green needles, plain white baubles can wash out completely, and you end up with a tree that looks half decorated even when it's not. It's still worth doing, because nothing else makes a tree look as calm, but go in knowing you need some texture or shine to stop it going flat.
The easiest shades to live with aren't pure white at all, they're the ones with a little warmth in them, ivory, bone, a soft antique white that doesn't fight with warm bulbs the way stark white does. Matte finishes read as softer and more forgiving, especially in a room with a lot going on already, while a few gloss or glitter pieces mixed in give you the sparkle that matte alone won't. If you've got nothing white yet, start with a set of plain matte baubles in two sizes, nothing fussy, no patterns, just shape and finish, because that gives you a base you can keep adding to every year without anything clashing. Buy the shapes, not the themes. A snowflake you love this year is a snowflake you're stuck with for the next ten.
This look sits best in rooms that already lean neutral, a living room with a beige or gray sofa, a hallway with white walls and a wood console table, anywhere the rest of the decor isn't shouting for attention. It's especially good in smaller apartments where a loud, multicolor tree can start to feel like a lot in a room that's also trying to be a dining area and an office. White ornaments calm a tree down instead of adding to the noise, which is why they work so well in rented places too, nothing clashes with a landlord's beige walls, and nothing dates the way a very trend driven color scheme does. They also carry past the holidays better than most decorations, since plain white glass or ceramic shapes don't scream Christmas the way red and green does, so they can sit out a little longer into January without looking like you forgot to take the tree down.
Would I still like this if every other light in the room went off and all I had was the shape and the finish, or am I just buying into the sparkle?