When comparing Ren'Py vs jMonkey3, the Slant community recommends Ren'Py for most people. In the question“What are the best 100% free and easy game engines for beginners?” Ren'Py is ranked 26th while jMonkey3 is ranked 27th. The most important reason people chose Ren'Py is:
Available on Windows, Linux, OSX, iOS and Android.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Cross-platform
Available on Windows, Linux, OSX, iOS and Android.
Pro Active and friendly community
Pro Reasonably good at creating puzzle and point-and-click games
Pro Java is a great development platform
Java is a well-optimized just-in-time compiled language. It's faster than languages without an effective native-code compiler such as Python or Ruby, similar in speed to other just-in-time compiled languages such as C#, while slightly slower than compiled languages such as C or C++ (with some low-level and numeric benchmarks being similar to C++).
Java also has a wide variety of high-class IDEs available.
Pro Multiplatform support
Code can be ported to mobile (iOS is in the works) and other Android supported devices with minor changes to the code (just change some implementations that vary on the platform such as inputs and user interface). It can even run on certain Raspberry Pi devices.
Pro Free and open-source
jMonkey is completely free, meaning it's possible to develop and release a game with no fees or royalties. Because it is open-source, jMonkey has plenty of people fixing bugs and, adding to the engine as well as creating a variety of plugins that can be used in the engine.
Pro Not limited to using its own IDE
Unlike some engines, jMonkey doesn't force its own IDE. You can use its Netbeans-based IDE, but you can also set up a project to work in another IDE such as Eclipse. You can still use the special tools from jMonkey's IDE in such projects.
Pro Engine modifications can be made using Java
Because jMonkey is implemented in Java, the same language its apps are typically developed in, developers will have an easier time modifying the engine to their needs.
Pro Has everything
jMonkey3 handles input from computers and mobile devices. It handles networking, physics, rendering, terrain, and cinematics.
Pro Ease of extensibility
Engine is modifiable.
Pro Freedom of choice for architecture
The user is not compelled to use any programming architecture nor standard in order to make a project working. JME allows the freedom to use what is best for a game.
Pro Offers both low-level and high-level ways of editing shaders
Modifying shaders can be done either via a visual tool called Shader Nodes or via GLSL that allow you to make your own shaders without the engine getting in the way or having to hack around to do so.
Cons
Con Not for every genre
While technically capable of creating 2D games in any genre, Ren'Py excels in creating visual novels and has a reasonable feature set for creating puzzle and point-and-click games. Other genres are best tackled by other engines.
Con Outdated Documentation and official built-in tutorials
Unfortunately, you will have to hunt relevant info on how Ren'py script works. The Ren'Py dev has the working tutorials on his Patreon, other than that you might as well just code in Python.
Con Requires knowledge of Python to use
Con Terrible API reference
The methods are not defined.
Con Not an engine for total beginners
While it's clear that you need to know Java first before using this engine, it is recommended that you have some programming experience as well. Most performance issues and memory leaks are more due to bad programming practices than the engine itself.
Con Slow release cycle
jMonkey3 lacks manpower to have a fast and decent release cycle.
Con Relies on archaic tool chain
jMonkey Engine uses Apache Ant for build automation, which is archaic and backwards, even by Java standards.