When comparing Buildbox vs UDK, the Slant community recommends Buildbox for most people. In the question“What are the best 2D game engines?” Buildbox is ranked 51st while UDK is ranked 73rd. The most important reason people chose Buildbox is:
Drag - and - drop editor without writing any line of code.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Drag - and - drop editor
Drag - and - drop editor without writing any line of code.
Pro Easy to learn
Buildbox is a drag and drop engine, making it easy for beginners to pick up. There are many tutorials available to help get you started.
Pro Has many game templates
Buildbox has 20+ different game templates including templates for platformers, racing games and Flappy Bird clones.
Pro Built-in support for ads
You can add banner and interstitial ads from multiple ad networks, including AdMob, RevMob, Facebook. They can work with Amazon's, Microsoft's, Google's and Apple's app stores.
Pro Develop once publish everywhere
Exporting iOS/Android/macOS/Windows/Steam/Amazon
Pro Cross-platform
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.
Cons
Con Incredibly Expensive
$99/mo for full functionality probably makes this the least accessible piece of game development software in regards to price, all with a very limiting feature set.
Con You are restricted by it's limitations
For example, you can only make certain kind of games.
Con Not very powerful
You will be limited to using templates to build games.
Con Subscription Model
The two more reasonable price points limit the functionality of a software already far less powerful than many more cost effective alternatives.

Con Very expensive
Buildbox has a 15-day trial version, after that a $2675 license to use it must be bought.
Con Stability Issues
The software has stability issues on Windows, with the preview window causing program crashes when simple functionality is added.
Con Superseded by Unreal Engine 4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.
