When comparing Spine vs Adobe Animate (formerly Flash Professional), the Slant community recommends Spine for most people. In the question“What are the best 2D animation tools for game development?” Spine is ranked 2nd while Adobe Animate (formerly Flash Professional) is ranked 8th. The most important reason people chose Spine is:
Spine provides integrated modules for 14 major engines including GameMaker Studio, Cocos2Dx, LOVE, MonoGame, Unity, XNA, Flash, HTML 5, libgdx, Corona, and more. Generic runtime libraries are also available for C, C++, Objective C, C#, JavaScript, Lua and ActionScript 3. Dozens of third party libraries support additional targets.
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Pros

Pro Integration libraries support most engines
Spine provides integrated modules for 14 major engines including GameMaker Studio, Cocos2Dx, LOVE, MonoGame, Unity, XNA, Flash, HTML 5, libgdx, Corona, and more. Generic runtime libraries are also available for C, C++, Objective C, C#, JavaScript, Lua and ActionScript 3. Dozens of third party libraries support additional targets.
Pro Simplified UI allows for an easy learning curve
No-nonsense workflow allows you to create your artwork in programs much better suited for the task like Illustrator and Inkscape for example, while Spine itself focuses only on the important task of skeletal animation.
Pro Allows for easy use of artwork from third party programs
Spine's developers provide scripts which makes exporting artwork from third party programs much easier to do.

Pro Community-driven feature roadmap
Esoteric Software maintains public Waffle issue trackers to help plan and prioritize feature additions.

Pro Funded via Kickstarter
Spine received resounding support from Kickstarter backers, beating its pledge goal by over 5 times. A second successful Kickstarter added meshes and other important features.
Pro Price high for this product

Pro Powerful tool
This program has developed AAA TV Series and Movies like Fosters Home for Imaginary Friends and My Little Pony: Friendship is Magic.
Pro Export to HTML5
Pro Interpolation between frames
Several ways to create animation and special effects: motion tweens, classic tweens.
Pro Create and organize layers
Layers help you organize the artwork in your document. You can draw and edit objects on one layer without affecting objects on another layer.
Pro Bone tool
Bone tool that enables you to link symbols together quickly and easily in a parent/child relationship commonly referred to as inverse kinematics.
Pro Easy to use
Cons
Con Spine Professional is expensive
Spine Essential includes nearly all features, except IK, weights, and meshes. Spine Professional is expensive, though it does give all future updates for life (Spine is updated very often).
Con Requires EVERY developer to have a license
Ever developer needs a license, not just the animator, or an overall license for the project. The license agreement is extremely restrictive.
Con Doesn't support gamemaker 2.3
Con No integration for lesser known engines
Spine does not directly support some game engines, such as Construct 2 or Clickteam Fusion.
Con No more support
Adobe ditched AIR which they will EOL at 2020

Con Exspensive
Flash can be priced at $999.99 on the official Abobe store.
