Am planning a 2 week backpack trip and will be carrying a handgun (as I do every day anyway). I have already researched applicable state and area law and concealed carry reciprocity so those are not factors in this post. In any trip where you carry everything you need, weight and equipment durability is a concern. I'd like your opinions on which of the following that I already own would be your preferred carry and the best balance of rain (and sweat) durability.
Glock 19 with 1 15 round magazine - 29.7 ounces
S&W M&P9c with 1 12 round magazine - 30.5 ounces (weighed with CT grips attached)
S&W 640 with 5 rounds and 2 speedloaders carried in side pocket of pack - 30.3 ounces (.357 loads would be slightly heavier)
Other options but either weight or rust potential probably rule them out: S&W 686, Kahr CW9 or PM9, Colt Detective Special, Walther PPS,
I do not want or need to carry a .45 or .44 mag or shotty, or anything other than 9mm or .38 or possibly .357