My cousin and I want to make a game in python and c++. That game will mainly be an RTS (real tine strategy) but we don’t know what game engine would be the best to make it on. There is Unity which doesn’t work on Linux without wine. Shiva 3D the browser based one, UDK. There was also Panda 3d which is open source and it runs on Linux. It supports HDR Lighting among other things as well. I am hesitant on Unity because I don’t want to have to install the unity plugin or make it run on Adobe 3D flash player as I don’t have flash.
If you want a native browser game, you’re looking at HTML 5, Flash or Java. There are others of course…
However, only HTML 5 runs truly natively, no plugins, but most people have Flash or Java. Blender can produce browser games using the Burster plugin, but again it requires a 3rd party plugin, which does have a license fee for encryption. UDK is powerful, but it has certain terms for the free license if I recall correctly.
You are in a Blender-related forum. The results of this poll shouldn’t surprise you ;).
If that are your requirements:
Usage of Python
Usage of C++
Genre: RTS (Real Time Strategy)
then you are far away from thinking about a game engine. It is true that the choice of the tools to use are quite early at the game development. But long before that you should create a design document.
It should detail your vision (goals and purposes). From that you can derive the feature requirements. This all is very high level and does not belong to any specific hardware and OS without a reason. A reason could be the target audience (e.g. IPad users, Linux-nerds) or a non-common device (e.g. the WII controller).
After the design decisions you can decide what tools you want to use. Python and C/C++ are tools not features.
That means your only requirement left is: Genre=RTS
I think all of the listed Game Engines will do that. As you posted here, my advice is: Blender 
I come from Unity. I used Blender only for my models.
But I tried one of the latest Blender builds with Harmony and saw the Candy branch thread here just a couple of days ago. And all that stuff amazes me. It convinced me to give the the BGE a serious try for my next game project.
BGE is still a bit rough around the edges. But it has a great and helpful community (I don’t like Unity’s community btw.) and a lot raw power. And you don’t have to worry about the assets pipeline because it is integrated in Blender. I also like the Linux support. Something which most commercial/proprietary engines don’t have.
I am rather interesting on that, due Linux support, but can Blender GE export games ready for Android and iOS?
First of all your going about this in the wrong way. Anyone who tells you to use blender without offering up solid arguments to back their choice is bias and is leading you in the wrong direction.
You need to answer a few questions before deciding on what game engine is best for you.
I won’t answer your question because this question has been asked and answered a million times in almost every forum. If you had taken the time to type your question in Google search, you would have discovered your answer quicker, and you would have seen the Wikipedia comparison of game engines. Don’t wast your time here. The information you get here may not be what you want, and you may end up learning the hard way. NOW, get Googlin, or Yahooin, or Bingin!
If this game is for learning game design and just having fun too then go with Blender. You cant beat being able to do so much inside one program. You have logic bricks for prototyping and Python for more serious game logic. You have a dedicated community with alot of ttutorials and resources.
If you feel you have a real idea and you and your cousin are capable of producing something of value then look at Unity or UDK. Unity is a sophisticated peice of software that really focuses on making the Artist a gaming rockstar with a great pipeline and component scripting.
UDK is the next level up with a larger learning curve. Just look at Unreal’s catalog of blockbuster games made with it.
Dont forget about Cryengine. Shiva has the easiest learning curve and will reach various platforms. Torque 3d is now open source.
http://www.maratis3d.org/. Maratis is pretty cool but may not hvae the support you need.
In the end you need to try out these tools and see what one makes you feel confident and productive.
UDK requires some extra software and/or a lot of Java knowledge. As it is mainly for fps’, you have to work around some issues when you want to make the game cross-genre. And the graphics possibilities aren’t as big as one would suspect (No real mirroring, etc.). Also you are bound to the Epic Games Licensing System while it is easy to workaround licensing limitations in bge.