This is coming from a 3D Artist viewpoint of the Stingray engine. I played around with it for a few days, and it seems really nice, especially instantly linking assets from 3ds Max to the editor. Editing materials is somewhat a cross between Unity’s UI for plugging in textures and playing around with PBR, and UE4’s Material Editor for further customization… It felt a bit clunky for me, but everyone’s learning curve will vary, thus making that con subjective (I think anyway). At first glance, I couldn’t find a node to plug in textures (as you would in UE), but then realized I had to use the “Property Editor” UI to do that stuff. (Also, to get to the “meat and potato’s”, e.g. Shader Graph Editor, you have to click on the “Make Unique” button.
I went in somewhat blind, which is why most of the learning experience was banging my head against a wall, but I did watch a few tutorials. If you used Unity and UE4, then Stingray will be pretty easy to jump into.
I love UE4 with all my heart… but, Stingray has some sweet snaps for level editing! 
Definitely a slightly more enjoyable experience. I also played around with the Post Process settings, which is easy, and intuitive just like UE. So nothing to really talk about there. The image below was a small scene I was making, to showcase in Stingray (and of course UE. (And no, I never finished it! haha, one day)).
