One thing I havn't seen mentioned here is recoil difference between the two weights. I know everyone nashes their teeth and wrings their hands about how nasty the recoil in from a 40 caliber. I havn't really done a real study on the difference between the recoils. I think I have shot one of two boxes of 165 grain target ammo through my glock 27 when I first got it. Then I purchased 180 grain Hornady's in self defense ammo and I always buy practice ammo in the same weight as my SD ammo so thats all I shoot through it now.
I think I have seen several people say that the 165 grain bullets have a snappier recoil than the 180 grains. Maybe thats another reason to use the 180 grains, they migth allow slightly faster follow up shots.
For me, I am taking the 180 grains for better penetration and I have confidence that they will expand. I do plan on switching over to the short barrel 180 grain gold dots next time I purchase SD ammo. I just have better confidence in the gold dots.
On a side note, I sent an email to Buffalo Bore asking if they had any plans to make a "standard pressure" 40 caliber load. They sent back a reply that that is something they are planning on doing in the next year or so.
Hopefully they make a 180 grain using the gold dot bullets, especially formulated for short (3.5) barrels. I'll be one of their first customers for that!