I only have the 2015 MBP 15" to test against, but to my ears the 12.9" iPad Pro 3rd gen speakers sound better. I tested both at half volume since it is late here, but the iPad Pro has a bit more depth, warmth, and bass. I'm not the best at using the proper terms to describe audio things as I'm not an audiophile, but consider myself an above-average listener who appreciates better sounding audio but isn't obsessed with the details. Anyway, the MacBook Pro did maybe a little better on the high end, but overall sounded more tinny and flat. I tested using electronic (Approaching Nirvana), rock (Foo Fighters), and classical/instrumental music (Inon Zur).