The method of attachment from the Lanyard to the anchor is critical. Details to look out for when selecting the carabiner would be the locking mechanism and the nose design. A clean nose prevents the carabiner snagging on the anchor as you remove it or getting hung up on the anchor when loaded. I’ve tested a hung-up carabiner and it failed at 3kN. Some great images and further info on nose hooked carabiners can be found here from Black Diamond and here from DMM.
For me it's the locking mechanism that is most important. The 8 karabiners in the photo at the top of the page have been the most common types of locking and auto locking mechanism. From the left;
Petzl OK Triact.
This is an automatic locking karabiner with a triple action gate opening (up, twist and open). Most manufacturers make a Triact style opening karabiner. Due to the three different planes of motion, it is unlikely (though still possible) for the carabiner to become accidentally unlocked. They are a little fiddly to use and a little more so if you are left handed. The nose is keylock which reduces snagging as you clip and unclip. 75g
DMM Sentinel Screw gate.
Standard HMS Karabiner with a screw gate barrel. The screwlock mechanism has been around the longest and is well tried and tested and most of us will carry these as the norm. The barrel can unscrew itself if the carabiner is repeatedly knocked or vibrated and grit/dirt/ice can impede the working of the barrel. DMM have created an Anti-Vibration screw lock (which came from use in Helicopters) to reduce the likelihood of the barrel unscrewing. Works well with gloves. 54g
Edelrid Pure Slider.
The new mechanism on the block. This is an automatic locking karabiner with a dual action opening (push in slide and open). This is by far the simplest mechanism on review here and it’s advantage is also its disadvantage – it’s very quick to open and close. It does come with a risk of opening as if you rub the gate up against the rock then the mechanism can be triggered and the gate opened. I find this really easy to use and have not had any issues with it accidently opening by rubbing against rope or rock and comes with a clean nose. The Pure Slide is one of the lightest locking carabiners made at 43g (Grivel Plume is 37g). Works well with gloves.
Edelrid HMS Strike Slider FG.
The HMS version of the Pure Slider, this has the added safety of an anti-rotation spring to prevent cross loading. Uses the same dual action opening action as the Pure Slider. This is the carabiner I use with the Kong Slyde and I really rate it. Works well with gloves. 66g.
Black Diamond Magnetron Vapourlock.
The Magnetron series come with two magnetic paddles embedded into the gate of the carabiner and two metal plates on the clean nose that engage with the magnets to lock the gate closed. At first, I was sceptical and thought of it as just a gimmick but when I first used it I was very impressed by the ease of the action. Though the release paddles look small they are easily opened with gloves on. Sadly, the nose of the carabiner is too wide to fit through the hole on the Kong Slyde (see photo below, but it does go through a Gri-Gri). Though I can’t use it with my Slyde as one of the lightest locking HMS carabiners made it forms part of my standard rack. 55g.
Grivel Twin Gate.
The Marmite carabiner of the climbing world. The carabiner comprises of two opposing gates hinged at either end. It has both the widest gate opening and is the strongest carabiner on review, it is also the heaviest. Those who love it seem to mainly like it for winter when screwgates have been known to freeze shut but the twin gate does not. Those who don’t like it find it fiddly to use especially when trying to remove from the back of the harness if you are an up clipper (like me). Stevie Haston has a video on Youtube showing how easy the carabiner is to open and close. For me its main disadvantages are that it doesn’t fit into my Kong Slyde or Gri-Gri and the nose is not clean. 85g.
Petzl Ball Lock.
Another 3 stage mechanism from Petzl, depress green ‘ball’ and then twist the gate to release the mechanism, open gate. Rather like the Triact system above, the advantages of the rapid auto locking system can be out weighted by the disadvantage of the fiddly opening mechanism. The Ball lock is certainly trickier to use with gloves on and a left-handed friend of my does find the twist is the wrong direction for him. Does have a clean nose though. 73g.
Mammut Crag HMS Slide.
This carabiner has tried to take on the disadvantage of the Edelrid Slide mechanism by enclosing the slide trigger in a plastic shroud so that it can’t be opened accidentally if pushed against the rock. The result is a carabiner that can’t be opened accidentally by the rock, but is very difficult to open with bare hands and nigh on impossible to open with gloves on. It does have a clean nose though. On my first outing with this crab i had it clipped to a sling on the back of my harness. Halfway up the route I wanted to poke the sling through as a thread. I got pumped silly trying to get it off my harness and then a further pump trying to clip the rope in with one hand. It was very close to being thrown into the sea below. This carabiner may work for some but it doesn’t for me. 79g.
Other karabiners to investigate would be the Via Ferrata K type carabiners, as these are autolocking and designed to be opened and closed at regular intervals. Examples would be the Petzl Vertigo Wire Lock karabiner and the Black Diamond Iron Cruiser. However, these are generally much heavier due to the extra strength requirements for Via Ferrata. I've written a previous post hereabout Via Ferrata Carabiners.
The Rock Exotica Pirate is an Auto Locking carabiner that can be changed into a non-auto-locking carabiner should you wish that.
When selecting a carabiner for your lanyard there are lots of choices out there. Personally, I use the Edelrid HMS Strike Slider FG because of its ease of mechanism with my Kong Slyde and the Petzl Triact with the Petzl Connect adjust because the rope runs smoothly over the round bar of the carabiner. Many Instructors prefer the screw gate mechanisms due to familiarity and trust. Each to there own, but which ever carabiner you chose inspect it as if you are constantly changing from cliping bolts to clipping metal then you may build up burrs on the inside of the carrabiner which may lead to damage when you clip soft materials (Rope, Slings etc)
I generally clip my belay carabiner to the back of my harness when not in use. Removing the auto locker from there was just a pain. That along side constantly having to undue the mechanism to clip the belay plate and then clip the rope in drove me mad. I persevered thinking that I might get used to it. I didn't.