Assign and edit keywords on images stored in the Finder. Apple does not allow App Store apps to modify keywords in the Photo library (!)
Store your images in cloud storage instead of Photos. Sync your edits, ratings, and flags across all your devices.
Remove noise using state of the art AI.
Erase objects using state of the art AI.
View and edit extended range images.
Export images at sizes above 100%
Greatly improved Perspective tool.
Remove haze from your images.
Add film grain or noise to images.
Put the viewer on a separate display from the thumbnails (Mac and iPad).
Import images directly into the file system or photo library.
Stack R+J pairs in the file system.
Write XMP into originals and flexible file extension options.
Teeth whitening, skin smoothing, eye brightening and more.
Advanced geotagging and location features.
Acclerate your workflow with Nitro-based shortcuts.
Edit both the image and video parts of a Live Photo.
Edit videos using Nitro's powerful tools.
Easier to use Masking interface.
I can't tell you everything :-) but there's a lot more...