Recs.
Updated
SpecsUpdate
Pros
Pro Lots of assets can be found in the Asset Store
For those developers who can't afford an artist, or aren't skilled enough to create their own art, Unity features an Asset Store full of a wide variety of free and paid assets that can be easily added to a game. The Asset Store has more than just music and art. It also has code and modules that can be added to games including unique lighting or GUI systems. It also has powerful asset management and attribute inspection.
Pro Lots of resources to learn from
Unity3D provides an exhaustive documentation where everything is given a full description supplied by a number of examples as well as video and text tutorials and live training sessions to understand the ins and outs of the engine. In addition there's an ever-growing community that can offer advice to help resolve any situations that may arise.
Along with the official Unity resources, there are many high quality (and often free) third party tutorials available.
Cons
Con Asset bundles can be cumbersome
Asset bundles are a way to load external resources that are not packed with the game or application and offered as a separate, optional package. However, they may not be compatible between versions or even platforms (you have to create them separately).
Asset bundles need to be loaded and unloaded, avoid concurrent loads from web or cache or a naming collision can happen. You can find workarounds with static objects (load obj
files and textures by code), but for animated game objects you are pretty much stuck with this.
Con Adds too many features without fixing earlier issues, rapidly increasing number of bugs that will never get fixed
Unity continues to add many new features without fixing earlier issues. Unity is either understaffed, overambitious, or both, resulting in a continual increase of problems and degraded experience across a number of platforms. Many bugs are reported daily and never get addressed, and there are many bugs from previous versions that are never looked at or fixed.
Con Encourages bad coding practices
A lot of Unity code feels like a hacked blur of arguable coding practices. C# and .Net usage in Unity is questionable. A lot of the API is done in "C Style" (public static methods, available at all times), encouraging the use of public fields for everything, a lot of questionable implicit casting. The list goes on.
Con Very self-centered engine
Unity3D uses very unique approach for doing things. Most of the knowledge acquired while using it, would be completely non transferable to other engines. Advanced Unity3D programming is really dealing with Unity3D bugs, and finding loopholes around engine issues - nothing to do with graphics, etc. Skills which would be valuable with other engines.
Con Hard to maintain projects due to vendor lock
Unity3D is proprietary, closed source game engine. Unity asks money for features like basic version control support, etc. It is impossible to migrate a game from Unity3D in case performance does not satisfy growing requirements of a project.