Have you already 3D art and assets, design docs ?

Caus that's not the engine that makes your game.
For example if i modelise with minimum 2D art, i know it will never reach a good model with good design and study.

Same thing if you can't have 3D artits working fast and producing today AAA characters with normal maps animations,
Artists making great levels and textures ....
The AAA engine won't make the essential graphics and 3D art for you !

Depends on your game , if it is terrain, some ennemies,some buildings, it won't ask you as lot of work as very studied levels, not only outdoor.
But Unity for example , that have complete terrain tools , amazing workflow , and that you can extend easily with C# could be an option for you.