When comparing Wave vs Unity 2D, the Slant community recommends Unity 2D for most people. In the question“What are the best 2D game engines?” Unity 2D is ranked 7th while Wave is ranked 33rd. 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 Extensive learning material
In addition to online API documentation, the Wave Engine team provides tutorials via IndieDB, plus sample projects and "QuickStarters" via GitHub.

Pro Supports coding in C#, F# and Visual Basic
Wave Engine explicitly supports all three core .Net Platform languages.

Pro Oculus Rift support
The Wave Engine team provides an official, open-source Oculus Rift extension via GitHub.

Pro Many components are open source
Several core components and official extensions of the Wave Engine are publicly hosted on GitHub.
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.
Cons

Con Mandatory splash screen
Games and applications made with Wave Engine must display a splash screen advertising it. No splash-free license option is available.
Con Not many tutorials available
Con Outdated UI
The UI looks like it is from Windows XP days. A refresh is much needed.
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.
