Liquidlogic Kayaks wrote an answer about Liquidlogic Kayaks Remix XP9 Kayak on February 4, 2013
Yes, their is less room in the XP 9 than the XP 10. The 9 is a foot shorter, narrower, and overall lower volume. If you typically wear small or medium clothing, you most likely fit in the 9. For example if you are shorter than 5 foot 7 and 150 lbs, this is your boat. If you are over 5 10 and wear large or XL clothing, you will most likely fit in the XP 10. Go bigger if you are planning longer trips. You can customize the outfitting for a more personal fit, but not everyone can achieve perfection in the fit if they are too small for the 10 or too large for the 9.
Generally, the 9 is for smaller and small medium paddlers and the 10 is for large to extra large paddlers.