Its all about what style of wave riding you want from your SUP?
Both sweet boards and both have different styles.
For me the 11'2 is longboarding at its best. And it catches anything from as small as a ripple to as big as you dare to take it out in.
Also for me the 9'8 is geared for shortboarding. Probably a bit hard to nose ride on but definately sweet for fast take offs and steeper waves.
Both being 30" wide which really only leaves the length as a deciding point?
Hope this helps