Great topic for some deep thought!
Of course, both are good, and sometimes every individual golfer looks for one or the other, no?
But I have always thought along the lines of Scott Warren - if a course allows or presents the opportunity to play a wide variety of "non standard" shots, to me its fun. These include the Cape or Challenge Tee shots, maybe an island green, shots off rolling lies, etc. (the thrilling kind) and also the run up and dainty chips, and occasional roller coaster long putts. Obviously wind and fast and firm fit in that for me.
Part of the fun formula to me is that if I try and miss, I am not making 8 on every hole. In other words, the hazards are fairly benign, shallow sand, vs OB, etc. Not all the time, just most times. Because being able to tell the story of playing out of the Da bunker at PV for instance, is also a great amount of fun.
Perhaps the gauge of fun is really how many bar stories the course tends to generate over the normal course?
For the record, to me, both Shinny and NGLA are fun to the max. Maybe NGLA is a bit more fun, even if some bunkers are deep. But, the museum piece quality of the CBM architecture kick it to a narrow fun win for me. Both ask you constantly to pick a line off the tee, and there is quite a bit of hang time between hitting and knowing the result for sure.