Masking is not nearly as easy to apply. It's very quick to get smooth edges in your mask in Photoshop.

Photoshop now has a built in AI (Beta Version) to generate backgrounds or add things to your image.

In GIMP, you can only use one artboard (canvas) at a time. Photoshop can have multiple within one file

Photoshop can link directly to illustrator and can handle vectors, not just rasterized images.

Most of the scaling and filtering tools just tend to work better in Photoshop. Also The "Object Selection" tool in Photoshop is amazing. This doesn't exist in GIMP.

Smart objects are nice too (Photoshop only) - makes it so you can edit one object and change it across multiple artboards + other functionality.

And one of my biggest issues, GIMP can't edit pictures in CMYK - it's a big work around just to try and export your sRGB image to CMYK in GIMP, but your colors will change.

Literally the only thing I like GIMP over Photoshop for is that it's easier to add gradients with a transparency

Edit:

Oh and gimp is good at changing specific color hues quickly. But that's all I've found