The way I look at it, if I can't record it on the negative, it can never be on the print. And slide film is a special case, with only 5 to 7 stops of range depending on the film you use.
If I take a camera out for nighttime street photgraphy, you can bet I'll be hoping for some wiggle room - in this case to ensure I get printable negatives at all.
The safe approach for exposure is to leave yourself some room; if you are making a negative of a scene with say 8 stops of brightness range, why not put the exposure in the middle, so you get a stop or so of insurance on each end? Making a succesful print is like going through a series of doors, each one smaller. If the errors are bigger than the doors, you eventually get stopped before you reach your goal.
As for me, my printmaking hasn't quite caught up with my negatives. But when it does, I'll have the negatives.:)
By the way, I like the sniper analogy. My father was sniper in the 36th infantry division in WWII, I've been a target shooter for about 40 years.
To return to a point in the original post, the OP mentioned having a metering app for his iPhone. In my experience, the free light meter app for the iPhone does a bang-up job of metering, provided you know how to use it. It's the rough equivalent of a 5-degree spot meter, and you can use it to very quickly determine the SBR of a scene by moving the metering circle around on the screen. It's not a Minolta, Sekonic or Pentax 1-degree spot meter, but it's something you can (and most likely will) always have with you. I don't know that I'd use it for metering really long exposures at night, but I haven't tried that yet. THOSE are scenes I do reserve for the good hand-held meters that I can calibrate.