Sharky here is why I stuck with Reality. I too was into UE and shaders ect. In spite of all that I saw IMMIDIATE improvements using Reality LUX. This one with a structure which mostly could not be hidden and as Paolo mentioned with some glossy settings set too high using the sun and few mesh lights took 2 /1/2 days back then http://fav.me/d4solzk.

These were  slg renders that took a few hours I then rendered the characters on their own in full LUX and PS'd them together http://fav.me/d4somlh  http://fav.me/d4solye I was experimenting and finding my workflow which of course is always ongoing.

Fast forward a few months in this more or less same type setting instead of using the sun I use one mesh light with the sun as a pre set to give the effect of the sun coming in with one mesh light above and a curve light to the side and this took 5 to 6 hours

http://fav.me/d519vv1

BTW the render with the ray gun took hour and twenty the one with the giant female 6 to 7...