Proper width is most important — over length. That being said, longer boards will usually make longer more gradual turns resulting in faster speeds. They float better in pow at lower speeds too. SHORTER boards turn quicker so they are better for maneuverability and places where that is important like trees and moguls.The lengths you mention don't seem too extreme one wey or the other, so it is something to consider.
thanks frosty. By the way, between Lib Tech Box Scratcher and Salomon Drift which is better for newbie like me? Im starting to do a few ground tricks and been thinking about kicker and park.