preference
I'm believing that since the OP is shooting Berry's (plated) already, he is inquiring about practice /paper punching bullets for reloading.
The 115's are a bit cheaper over the long run, 2-3 bucks per 1000. That's not much, but is money that could be spent otherwise, ....primers, match fees, whatever. The 124 is the classic 9mm weight, and I wanted to go that route with our 9mm's, but the couple of bucks saved lured me to 115's.
I can't tell the difference between 115-124, but lots of guys tell me that 147 can be loaded to "make major" and be a good bit softer to shoot than the lighter weight slugs for match use.