The following are some of the things we have learned about purchasing these popular items:
1) Longer is more stable at speed and the shorter will be easier to turn. However, this type of "ski" is very easy to turn anyway.
2) Almost all skiboards are made out of the same materials as skis and snowboards. You'll find most models to be very light and easy to use for tricks. There is some wood inside many of these but it's only a part of the construction. There are many other lighter materials as well.
3) Wider will be slightly more stable but maybe a little tougher to turn. What is equally important is the sidecut. A deeper sidecut (difference between the tip, middle, and tail measurements) will result in more of a carving action when the skiblade is put on edge. Look at the full dimensions of the skis as the tip, waist and tail usually have different dimensions. For example, the Salomon Miniverse is Length 90 cm and sidecut 100/80/90. The tip is slightly wider than the tail. This is also for turning ease.
Salomon is the premier manufacturer in this category of product. We are also very happy with the K2 Fatty and Line skiblades.