Pixelmator vs Piskel
When comparing Pixelmator vs Piskel, the Slant community recommends Piskel for most people. In the question“What are the best pixel art / sprite editors?” Piskel is ranked 7th while Pixelmator is ranked 11th. The most important reason people chose Piskel is:
WPiskel is HTML5-based so it works in any modern browser.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Beautiful, easy to use UI
Pixelmator's interface is pleasant to look at, easy to use and specifically optimized for OS X users, making it very intuitive for long-time Mac users.
Pro Feature rich
Not only does Piexelmator provide easy to use tools that you should expect in any image editor, it also has rare tools such as layer styles, liquify tools and OS X optimized, fast image manipulation engine among others.
Pro Supports layer styles
Layer styles allow non-destructively applying effects to a layer.
Pro Powerful effects
Dozens of visual effects available, easily discovered from the visual Effects Browser, broken into categories. Effects have interactive dialogs and live preview.
Pro Multiple-display support
Pixelmator can be used across any number of monitors.
Pro Loads quickly
Gives you common image editing capabilities almost instantly.
Pro Great performance
Pixelmator's image engine is specifically optimized for use with Macs, providing one the best performance results available on OS X.
Pro Inexpensive
Pixelmator costs just $30 on the App Store. Additionally, it often comes bundled with other software that you might also find useful bringing the price down.
Pro Works in any browser
WPiskel is HTML5-based so it works in any modern browser.

Pro Animation support
Piskel includes onion skinning, exporting to sprite sheets or gifs, defining frame rate, and present live playback.
Pro Sleek interface
It is also easy on the eyes.
Pro Very simple for beginners
Once you get the hang of it its a very powerful tool
Pro Offline versions available
The downloadable version of Piskel (built with node-webkit) is available for Windows, Linux, and Mac OS X.
Pro Easy to use lighten and darken tool
With the click of a button you can create amazing shading.
Pro Enough tools to be powerful
It has enough tools to be powerful, but not too many to put off beginners.
Pro Open source
Piskel is licensed under Apache License, meaning that the user can use the software for any purpose.
Pro Has a straight foreward tile view mode
... so you can instantly see the result while drawing tiles
Cons
Con Lacks a true resizing tool
There doesn't seem to be any decent tool in Piskel for an easy stretch or shrink. The only ways possible is resizing the whole image or importing and image and shrinking it from the export tool.
Con No button for undo
Have to use ctrl+Z.
Con Rotation is limited
Rotation is only made in predefined angles. Does not support variable rotations or mouse based rotation. Does not support rotating selected areas, only frames-layers.
Con Shading by hand
Shading can be difficult.
Con Doesn't work well with drawpads
In the online tool you can't draw lines at all, yet using a graphic tablet, being in the offline version controls are pretty chunky and everytime you start drawing a line, the screen flickers black for a short period of time.
