I've been working with the XNA-Framework(only in 2D) for over a year now. Now I want to try and start a bigger 3D-project. But somehow I have difficulties to decide which engine/Framework I should use. So far I gathered three possible Frameworks, I want to list here:
XNA with the OX-engine: I already have some experience with XNA and the Ox-engine seems to be the best possible open source engine I could use here.
OGRE-engine: Always wanted to get a little deeper into C++ and the engine seems to be well documented.
Cryengine/Sandbox 2 or higher: Well this one also needs C++ knowledge, seems to be user friendly and lets face it one of the most powerful engines out there.
My goals are to start learning 3D-programming and to realize first 3D projects by taking baby steps.
So the question is what engine would you guys recommend? Is there any other stuff I have overseen? as mentioned before getting a little more into C++ would be great to but it is not a "must have" as I alredy worked with C/C#. Most important to me would be that I could lear stuff that I can use later on for example in other Frameworks. This is important to me because I want to get deep into one thing I will be doing for a long time.
Thanks in advance!

