Mountain bike shorts are available in a  variety of Styles. We recommend that you first consider what type of riding you are going to do most often and what type of features you need for that type of riding. We recommend buying a short with features you will use and nothing more. 

For cross-country Riders most will want a not too long short maybe Just above the knee as with Enduro or DH riders who tend to wear Knee Pads a Slightly longer Short will feature better.