I don't vary because all my SD HGs have night sights and I carry a 80 or greater lumen pocket light day or night too. Inside buildings with little or no light are often more challenging than nights in general.
Same same. XD40 4" crimson trace grips, no night sights, two mags. Surefire g2 led. Occasionally include my S&W 642 with crimson trace grips.
Armsmaster, sweet carry pieces
Day/Night - Same Thing (Gun changes depending on where I'm going)
G22 .40S&W, S&W 642CT .38Spl +P, or G20SF 10mm
Sometimes the 642 as a BUG
Spare Mag or Speedloader
Browning Tactical Hunter 210Lumen LED
Kimber Guardian Angel
Kershaw 3" Folder
CRKT 2.5" Assisted Opening
Cell Phone
Everything has night sights, I make choice based on ability to conceal and whether I want hi-cap. Day/night is irrelevant.
"More than likely you won't be using your sights in a SD situation."
I try to get at least my front sight on target while practicing. Of course if you are contact close not a worry.