Thought this might be of interest:
http://www.jimwaltonmia.com/single-post/2017/12/01/Review-of-Auto-Locking-Karabiners---for-use-with-Lanyards

Mike

I use klettersteig krabs on ends of cowstails. Massive capacity and opening, narrow enough end for holding and to seat the knot. They are straight-pull ones, so don't foul up much in mud and grit. I've never got on with the multi-action ones even out of caves.

This is the modern version:

Mine is all-metal and without the protruding bit on the gate.

As above: just about perfect for cows tails ?

Yep, if you fancy an extra-secure cowstail, Via Ferrata carabiners make a lot of sense. They are very much designed for this job.

Personally I've always preferred the "thumb trigger" type. I've used CAMP Hercules carabiners; some modern versions look even slicker, being designed so you can open the carabiner without your thumb obstructing any of the gate opening:

https://www.youtube.com/watch?v=ozxHZe3Dl4E

(PS, anyone spot the Bad Practice in that video?)

Via Ferrata carabiners are much chunkier than the ones we normally use in caving. Depending on how you do SRT, this may be relevant -- particularly when connecting them to hand jammers, where they don't fit properly in the smaller holes.

I use double action twist locks on my cows tails; I am happy hanging on just one. I don't use double action twist locks anywhere else (except bag tethers). Triple action is too much faff for cowstails although I use them elsewhere extensively.

(double action = twist, open; triple action = lift, twist, open)

I find the Petzl Triact triple action pretty reliable as long as you keep it cleanish. I have cowstails with DMM Shadow (double action) twist locks and Petzl Am'D (double action) twist locks and find both fine.

DMM triple action twist locks are, however, horrific underground and start failing to lock closed almost immediately on contact with mud. Great above ground though.

I'm a professional user and have Via Ferrata Petzl Vertigo karabiners on my own set up. They are very convenient.  They need a little maintenance in the form of washing and  GT85 and/or WD 40, occasionally.

Client SRT kits are set up with screw gate karabiners on lanyards. The self locking connectors are Omni - Petzl Triact and Petzl Freino twist lock. These need to be washed and lubricated on a regular basis.

I work in pretty dirty places so cleaning and maintenance is a key safety issue.