Help Deciding Which Sling is Best for You
Slings are roughly divided into categories based on the number of points of contact with the marker, 1, 2, or 3.
A 1 point sling is attached at a single point, usually near the stock. Because this greatly limits control over your gun these aren't used terribly frequently in paintball, but do offer the highest degree of mobility of the three. An ambidextrous player or one looking to switch arms frequently might prefer a 1 point sling. A 1 point sling is usually worn over one shoulder and under the opposite arm.
2 point slings attach at two points to the marker, usually at or near the stock, and at or near the barrel. A 2 point sling is primarily used to hold the marker while letting your hands free, say to toss a grenade or reach for a sidearm pistol. Slings often are a compromise between versatility and ease of use, and the 2 point sling sits comfortably in the center of these, which may be why it's usually the favored sling.
3 point slings still attach at two points to the marker, but also loop back around and attaches back to the first point, allowing the straps a high degree of customizability. With a 3 point you can hang your gun behind your back almost like it's a backpack if you need to climb to a better position, and the sling can also be used essentially the same as a 2 point sling. This versatility comes at a cost, though, because the doubled-back loop means there's a lot of sling wrapped around, and you can easily get tangled up in it.