Sketch vs Krita

Sketch is essentially a version of Photoshop built from the ground up to suit the workflow of web designers.

Sketch is hugely popular among designers so there are a lot of well maintained community resources for everything from iPhone frames to iOS/Android UI elements & icons.

Reactive panels keep the UI for Sketch clean from the sort of clutter the panel system in Photoshop suffers from. The panels in Sketch change based on the object in question, saving you from having to have a multiple separate panels.

Sketch lets you re-use the same design in multiple places, with changes synced throughout the various places it is used. You can also create text styles to sync typography changes.

Artboards let you easily work on multiple views side by side. Great for having a separate artboard on each page for the various responsive sizes.

You can rescale assets without quality loss, easily export x2 assets for retina designs and design high quality icons & artwork. Being pixel aware lets you set a grid and snap objects to it as well as round to the nearest pixel edge to clean up your layers.

Sketch has a built in exporter that supports PDF, JPG and PNG.

You can set the square grid to whatever dimensions you like as well as set thicker lines every x blocks. You can also configure the color of the lines to make them as obvious or subtle as you wish and toggle the grid with a keyboard shortcut (crtl+g).

Mirror lets you connect your iPhone to sketch and see how your current artboard looks on mobile. It's really useful as you can live check changes which lets you rapidly iterate mobile design.

Holding down alt will show the smart guides that show the distances between any layer you hover over to nearby layers or the edges of the artboard. Very useful for checking your spacing or aligning layers.

All the most used and useful tools are easy to find in Krita's UI and are often just one click away. They are not hidden behind menus or dropdowns.

Krita is getting constant releases with updates and bug fixes. New features are added at a pace that far surpasses the other alternatives.

Krita is completely free and open source. They have raised a couple of successful Kickstarters in the past to get the initial financing and now they are accepting donations.

KDE has a long history of making solid applications.

Krita's preset brushes are one of the default dockers. Each brush has a preview on mouseover that shows a detailed view of the type of brush involved. All the brushes also have useful and descriptive names such as "HP Pencil" or "Textured Fuzzy".

Although the UI is rather busy, Krita is very customizable. The editing window can be themed and the sidebar can be customized extensively throw many dockers or panes.

Tiled view that shows your image tiled in the editor, and permits you to edit it as you are seeing it tiled. If the brush passes out of your texture, it will just automatically wrap back the painting to the other side of the original texture, while permitting you to paint and see the results on any of the tiled "clones" (the shortcut key to activate this is w by default).