If your pistol has fixed sights, it may well be regulated to place the standard 180-grain loads at point-of-aim. Lighter-bullet loads may have a different point of impact. Any reasonable bullet weight can be driven at a velocity that will cause significant damage to a living target, but shot placement can be important, as not all armed encounters are at arm's length. I use 180-grain Gold Dots in my SIGs. I wear a badge, and am more likely to defend another person, and/or be dispatched to trouble, which will mean I may seek cover at some distance from an adversary upon arrival. 165-grain ammo impacts notably lower than 180, but is still close enough to be an OK substitute. (I must buy my own duty ammo, within guidelines.) 155 is starting to get really low at 15 yards, and is noticeable at shorter distance.
If one uses 135-to140-grain ammo, it might be a good idea to see where it impacts at something like across-a-parking-lot distance.