The Pro Savannah XL is more closely related to the 9 series as they are made from the same material. And the length of the Pro Savannah XL is slightly longer than normal racket, that would be the same as the racket that is design for playing Singles.
The new Nano Power Savannah is made of the Nano material that create a stronger ultra-light racket. For hard hitter player would definitely appreciate the stiffer shaft this racket have.
The 919 racket has a wide body frame (or muscle power frame), and is suited for a defensive playing style.
The 929 racket has a slim body frame, and a vibration filter on the shaft near the handle. The slim body frame design is suited for attacking play and the vibration filter will give you easier spin and directional control of the shuttle.
The 939 racket has a slim body frame, and have extra grommets (76 grommets - normal racket have 72) to give more strength to the string. Suitable for attacking play.