Yes, it does matter.
When youd like to educate yourself instead of shooting down things you dont know anything about, post up! Congrats on the purchase!
Hmmm. I've been shooting, teaching classes, and studying ballistics ever since I first started carrying a handgun nearly four decades ago--I'm going to have to side with JGulley on this one. The advantage, if there is any, to using 124 grain rather than 115 grain bullets is minimal--certainly not enough of a difference to warrant the above comment.