If you plan to use your Roller in a single location -- e.g. at home -- you'll love the full-size model, because its extra length makes it more efficient for performing many exercises. It's long enough to roll the widest part of your back in one pass; you can roll both legs (quads, hamstrings, and/or calves) at the same time; and you can even transition from one IT band to the other without moving the roller. With the Compact Roller, you'll need to roll each leg separately, and will spend a little more time repositioning yourself between exercises. The major advantage the Compact Roller has over the full-size model is its portability. it fits easily in your gym bag, backpack, or carry-on luggage. This makes it a favorite of many runners and triathletes who transport theirs from race to race. The Compact Roller's smaller diameter allows it to conform better to the curvature of some body parts, such as your neck. If you're new to foam rolling or have gotten positive results from any type of conventional foam roller, you'll want the original density. Even though this is our "softest" roller, it's still more aggressive than any other foam roller on the market. The extra-firm version is intended for experienced users with especially dense muscle tissue that doesn't respond to normal massage pressure.