Can't wait to see some of your renders!

I'm leaning solidly towards Thea Render because it's got an unbiased engine and it has a "studio" version that doesn't require a completely separate poly app just to render Moi creations. It also is the "next up" from the free Kerkythea renderer I've used for a few years now. It's materials are also easy to deal with.

But there are other rendering apps I find to be adequate.

I've come to find that really it has more to do with the 3D modeling program a designer uses as typically, the rendering is done as a peripheral to their modeling environment.
So with Blender, you can use Cycles, with 3DS Max, Rhino and etc, you can use all kinds of 'third-party' renderers. I really found V-Ray to be appealing.

Aside from UI and ergonomic creature-comforts, and aside from polygon and material handling, I'm hoping that somewhere out there someone has done a thorough comparison of each rendering platform (and method engine.) I'm sure they exist. It would be nice to see with the eye which one blow you away with its realism and which ones look 'fakey'.

Render result quality is also very subjective I know; from interiors to exteriors, differences in the rendering and presentation intent of the scene.
Renders that look superb for stunning interior architectural scenes would not work so well for showing the nuances of a killer product shot. And the same for animation.

I suppose, it would be equally as hard to discriminate between the better modeling platform... to each his own.