Let’s start with the simplest and probably the most common system, single rope. As the name suggests you climb with a single rope clipping all your pieces of gear to the one rope. This is the system we normally use for sport climbing, trad climbing and some alpine climbing. Its advantage is in its simplicity and is best suited to straighter routes but it does mean only short rappels (unless you carry a tag line).
My favorite rope for this type of climbing is the Sterling Fusion Ion 9.4mm. This rope has the bi-pattern feature meaning the middle of the rope is easy to find as the pattern changes. There are skinnier and also fatter single ropes but the Ion offers great balance between weight and durability. As a guide this is an important balance as I am often belaying two of these ropes at the same time. Get one too fat and I have to visit my physio with elbow problems too thin and I have to replace my rope often!
Half ropes is a system you should get familiar with if you are a frequent ice climber, someone who enjoys wandering trad routes or likes sketchy rock. Half ropes mean you are always tied in and belayed on two ropes but you only clip one strand of rope to each piece of protection. These ropes are pretty skinny from 9mm – 8mm and because of the width they stretch a lot! This means they reduce the amount of force that is applied to pieces of protection, which can be a critical factor when you are talking about ice screws, or other marginal protection.
Another bonus is the long rappel of having two ropes with you. A lot of half ropes these days are rated so that you can second on a single strand, but think hard about whether you want to be hanging from 8mm of rope with 1000ft of air below your feet. My half rope of choice is the Sterling Evolution Duetto 8.4mm. Although skinny and maybe not wearing so well if used a lot in the rock realm, I mostly use this rope for ice climbing when I want the minimum force going to my anchors. A nice thought with half ropes is this. I have 16.8mm of rope attached to me, which makes me feel pretty safe!
Twin rope is the final and very euro rope technique (I am allowed to say this being from Europe). For this you tie into two ropes just like half ropes but unlike half ropes you must clip both ropes to all the pieces of gear. The advantage of this is you get to split the ropes between two people and get to carry a super skinny rope like Sterling’s Fusion Photon 7.8mm and you also get the advantage of a long rappel.
So what is the best system? Well that depends. Every climb presents different challenges and deciding which rope to climb on to give you the most safety, speed, versatility and efficiency is up the individual to decide.