When comparing UDK vs GameGuru, the Slant community recommends UDK for most people. In the question“What are the best 3D game engines?” UDK is ranked 17th while GameGuru is ranked 38th. The most important reason people chose UDK is:
UDK has an extremely large toolset that allows creating almost anything without having to use a 3rd party tool or plugin.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Large toolset
UDK has an extremely large toolset that allows creating almost anything without having to use a 3rd party tool or plugin.
Pro Triple A track record
UDK is an engine used by many big name companies for popular games such as the Gears of War series.

Pro Designed for ease of use
Simplicity and accessibility are the core design goals of FPS Creator Reloaded.


Pro Active and helpful community
Users share ideas, help, and advice through the official forums. The community also provides a wealth of free assets, and the GameGuru Assets Store sees constant additions.

Pro Continuous development and updates
News and improvements are released on a monthly schedule. Interaction between The Game Creators and project backers is excellent.


Pro Awesome tech support

Pro Easy to use your own custom assets
Easily import your own 3D models with the built-in importer and create custom characters with the Character creator. Custom weapons are much more difficult, though.
Pro Massive community of users
The gamer creator forums have a large number of users, developing games, making models for sale and to give away for other users. They answer questions, help each other with problems in their games, and can make using this software so much more fun and easy.
Pro Royalty free
Games you publish with GameGuru can be sold without any restrictions or commissions.
Pro Easy to use editor
An easy 3D editor to create your own maps in seconds with drag-and-drop function.

Pro Friendly GUI
Awesome friendly GUI, and quite easy to use.
Pro Building editor
Currently in development but already looking very good! Easily create big and customized buildings with default building blocks and share them with others.
Also very easy to use in the designer: The buildings are treated like entities but still directly available in the 'building editor mode'.
Pro Powerful scripting language
Uses Lua.
Pro Large asset store
A store where you can buy various assets for your games like sounds, 3D models, weapons... Very good prices and a lot of assets are even free.

Pro Feature priorities are chosen by the community
The Game Creators team frequent the forums and ask the community for feeback and suggestions both there and via an open poll on the website. They have a great history of reading suggestions, viewing screenshots, and generally working with the community.
Pro Optimised engine for editor
The game engine is optimized for efficient use of memory.
Cons
Con Superseded by Unreal Engine 4
Con DevKit only runs on Windows
Even though UDK can deploy games to run on multiple platforms, including Mac, it does not feature support for development on Mac.
Con Limits games to FPS
UDK was originally developed for the FPS, "Unreal Tournament", and it certainly shows. While UDK is a very powerful engine, it takes quite a bit of work to make it do something other than an FPS.
Con Slow
Everything takes ages..feels like Unreal 4
Con Lack of user-interface
Although you can customize a lot, the user-interface does not show that. But plans are in place to improve this with some front facing GUI into the LUA scripts so you don't need to code as much.
