Nightwear is one of the few wardrobe categories chosen purely for yourself, which is exactly why the print-versus-plain debate is worth thinking through.
The case for prints
Florals, polka dots and abstract prints add a sense of cheer to the bedroom and are a little more forgiving of the odd wash-day mark or stain. They also tend to hide light-heat marks from ironing better than solids.
The case for plain, solid shades
Solids photograph better for social sharing, mix and match more easily with robes or shrugs, and often feel a touch more premium and calming for a minimalist bedroom aesthetic.
A middle path: tonal prints
A subtle tonal or self-print - print and background in close, related shades - gives texture and interest without the visual busyness of a high-contrast floral.
Match it to your room, not just yourself
If your bedroom decor leans neutral and calm, a bold print can feel like a nice contrast. If your space is already colourful, a plain or tonal nighty balances it out.
There is no rulebook here - the best choice is simply the one you reach for most often.