Skunk. I think the key to that question is this. What grain ammo are you using for carry? If you are using 124gr for carry then buy and practice with 124gr.
It's rarely going to be perfect but with the same grain projectile as long as they are close in velocity it should be close enough for government work
If you plan on burning a ton of ammo 115 is occasionally cheaper. But I am finding they are pretty close in price and I shoot a lot so I buy in bulk anyway. I also use 124 gr. More because it has a little more umph on steel plates and a marginal hit may knock it down where a weaker ammo with 115 may not. It's not a big difference but it has won me braggin rights a few times.