- Photopea's UI is very similar to Photoshop - same tool layouts, similar iconography and even has the same keyboard shortcuts, which makes a seasoned Photoshop user feel right at home. And while you can make GIMP look somewhat like Photoshop using thirdparty scripts (like PhotoGIMP), it still falls short considerably. In some ways this is even worse as it leads to an "uncanny valley" scenario.

As for Krita, its UI is of course a lot better than GIMP, but unfortunately it's mostly skewed towards digital illustration and art creation (and it's great at it!), but less towards photo editing/image manipulation.

- Photopea has the best .PSD support of the three, which is pretty crucial for people wanting to switch from Photoshop.

- Possibly the most important feature that Photoshop users depend on these days is Content-Aware Fill and Magic Replace for object removal and background patching. GIMP lacks native functionality for this (although there are thirdparty plugins, but I haven't used them so can't comment on that). As for Krita, once again Krita lacks these tools - and most retouching tools in fact - as it's more geared towards digital art creation rather than image manipulation.