My own personal preference would be to use Marmoset/Xoliul Shader 2/ 3PShader for a single assets. Simply because they don't compress textures, so you can get really close and not get any issues with artifacts etc. For levels I would use a game engine like UDK or CE3 as they are much more versatile in that regard and are…
if you want to use udk ...you can learn this http://www.polycount.com/forum/showthread.php?t=75364 :-) Ryan James Smith did very2 good job explaining noob like me how to make good instance material, once created, you can easily switch texture images and adjust the parameter just like marmoset
more importantly, go with what you know well. Dropping a great model and textures into udk with a simple phong material on them and default map lighting will quite often undersell your model. (unless you built and textured it with that in mind) If you feel comfortable tweaking the heck out of Xoliul's shader, use that. If…
I would say showing the best results would be the best. Unreal rendering has a certain 'aesthetic' I find that it's very well suited for. High value contrast, very sharp crispness to the textures. But for other things, Marmoset is possibly better for. Others I would say the CryEngine is better. I oftentimes find there's…