Most of the time, the lampshade should be bigger than the lamp to make the whole thing look balanced and nice. A lampshade's purpose is to spread and direct light, as well as to add to the lamp's general style and look. Here are a few reasons why it's best to get a bigger lamp shade:

Light distribution: A bigger lampshade lets the light spread out more widely, making the lighting in the room warmer and more natural. If the shade is too small, the light may be too strong and focused.

Visual harmony: A lamp with a small shade may look out of balance and out of proportion. The size of the lamp base can be matched by a bigger shade, which can make the whole thing look better.

Style and design: A larger lampshade can show off its shape and texture better, which adds to the lamp's general look.

Practically speaking, a bigger lampshade can also cover and protect the light bulb and the area around it better.

But it's important to think about the style and form of the lamp as well as what it's going to be used for. There may be artistic or practical reasons why some lamps have smaller shades. In the end, the size of the lampshade will depend on the person's taste in style and the lighting needs of the room.