Really ? I image this could be possible if you for example used ground plane (vray infinite), then regular one would trace it, but simple one ignore, and simply use VraySky which is super-intense even bellow horizon, so you get that "above clouds/skyscraper" type of lighting into room.
But if the difference is that big nonetheless, then they once again have documentation that absolutely sucks and the functions do things they're not well described. I have no patience anymore to do comparison so I can figure what does what.
I like Corona's implementation (well not the mat, it should be light instead) in that it does what it should, just focus rays, not create analytical light out of outside's environment intensity (then I can just create regular area light and map it directly I guess).
But both renderers got quite efficient that portals are becoming less of an necessity than they were.
