When comparing Unity 2D vs GAF:Flash to Unity, the Slant community recommends Unity 2D for most people. In the question“What are the best 2D animation tools for Unity?” Unity 2D is ranked 1st while GAF:Flash to Unity is ranked 9th. The most important reason people chose Unity 2D is:
2D game creation was a major feature request from the Unity community and was added with version 4.3. 2D is provided in both the Pro and Free distribution of Unity.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Built into Unity 4.3+
2D game creation was a major feature request from the Unity community and was added with version 4.3. 2D is provided in both the Pro and Free distribution of Unity.
Pro Integrates with Mecanim
Mecanim brings state machines and blending to 2D bone animation. The state machine editor allows for designers and programmers to visually create a Finite State Machine (FSM) to control when animations should play. Mecanim also allows for blending so an animation can transition smoothly between two states without the need of in between frames made by an animator.
Pro Sprite Sheet and Bone based animation supported
Both types of 2D animation for game development are supported in Unity’s system and can be used interchangeably in the timeline.
Pro Easily change sprites dynamically
Usually used for character customization, programmers can change any sprite in a bone animation at runtime easily by referencing the bone and loading the new sprite from the resources folder.
Pro Can convert 99% of what can be done in Flash
GAF supports such Flash features as:
Masks support;
Filters support;
No limitations on timeline;
Conversion of shape tweens;
Frame labels.
Pro No need to use large Sprite Sheets
With GAF converter you get a highly optimized texture atlas and a config file. You don't need to take trouble over cumbersome sprite sheets. You can easily modify an already working in Unity animation and play around with the animations parts whenever you need.
Pro Alows using Flash animations in Unity
You can convert Flash animations directly in Unity with the help of plug-in. The converted .gaf file consists of a texturte atlas and a binary config.
Pro Supports different frameworks
Full playback API supported in Unity3d, Cocos2d-x, Cocos2d, Starling.
Pro Light, fast, and optimised
GAF is lightweight and fast in a project.
Pro Uses dynamic text
GAF can use dynamic text in animation on some platforms.
Pro Can customize sprite animation
GAF can swap a sprite with another.
Cons
Con Lacks critical features
- Vertices can't be animated, so you can't have ANY organic feel (like... lungs breathing).
- Parent bone can't be animated without affecting the children. This is especially impeding for organic feel, again.
- No option to show & unshow assets (or it is hidden), like for switching weapon on your character for exemple.

Con Poor script interface for texture atlases
Accessing individual sprites within an atlas texture is possible at runtime, but requires use of the Resources folder subsystem.
Con Sound support available only in Premium version
GAF Converter supports sound but only in the Premium version.

Con Doesn't support sounds
GAF does not support importing audio along with Flash animations.
