My dd has 2 of the 2014 models. She went and did some swinging with a new one when they first came out. To me the sound still sounds the same, but when you catch the ball on the sweet spot it does make more of a thud sound, but I think the 14 does the same thing. My dd just prefers the 14' over the 15'. If your dd is confident with the 15' model swing away. Just like my kid, she has it in her head that the 14' Xeno is the only bat on the planet right now, and it gives her the confidence she needs to go up to the plate and pound the ball. Needless to say if your swing is mechanically correct any bat will work..... just don't tell them that! In my opinion the Xeno is the best bat out right now.... but you know what they say about opinions.....