Are you sure the 9L has night sites? The only one I have seen had standard sites. The 4.25" Pro does come with night sites for sure and runs about 585.00.
Let me clarify a bit. Here's the 9L
•Model: M&P
•Caliber: .9MM
•Capacity: 17+1 Rounds
•No Magazine Safety
•3 Backstraps
•Barrel Length: 5"
•Front Sight: Steel Ramp Dovetail Mount, Tritium Sights
•Rear Sight: Steel Novak Lo-Mount Carry, Tritium Sights
•Trigger Pull: 6.5 lbs.
•Trigger Travel: Rest to Fire .300 in.
•Trigger Reset: Approx. .140 in.
•Frame: Large
•Finish: Slide and Barrel Black Melonite, 68HRc
•Overall Length: 8.25"
•Material: Zytel Polymer Frame, Stainless Steel Barrel/Slide and Structural Components
•Weight Empty (No Mag): 25.2 oz.
•Overall Height: 5.5"
•Width: 1.2"
$465
Here's the 9 Pro Series
Model: M&P9
.Caliber: 9mm
.Capacity: 17+1 Rounds
.Barrel Length: 5" / 12.7 cm
.Action: Striker Fire
(Double Action Only)
.Front Sight: Novak® Fiber Optic Green
.Rear Sight: Novak® Reduced Glare
.Trigger Pull: 4 - 5 1/2 lb.
.Weight: 26 oz / 737.1 g
.Frame Size: Large
.Overall Length: 8.5" / 21.2 cm
.Grip: (3) Interchangeable Palmswell Grip Sizes
Polymer
.Material: Polymer Frame/Stainless Steel Barrel and Slide
.Finish: Black, 68 HRc
$580
Look's to me that other than the sights, it's the trigger pull.