Here's the questions you need to ask yourself:
Why are you shooting 9mm in a carbine?
To get the most velocity out of the round? 115gr will be faster.
To get the most distance out of the round? 115gr will shoot flatter.
To get the most accuracy out of the round? Try a few different weights and brands to see what shoots the best in your gun. In my guns chambered in the same calibers, one gun often 'prefers' a different ammo brand or bullet weight to another brand or bullet weight.