What I find most important is making sure the person making the decision has the most amount of data to make the best/most educated decision possible. If you are comfortable with the risks/rewards and dangers to a given scenario (and everyone else with you is equally comfortable), then good on ya.
As far as biners, this even more so comes down to personal preference- it’s the kind of topic like which kayaking is better- creeking, playboating, big water, or _____ (insert topic here). Have a few beers and talk with your buddies about it.
Babbling about Biners:
If your system is rigged properly, then the biners should not be the weakest link in your system. The largest hazard one typically talks about with biners and boating is accidentally getting clipped into something you didn’t want to be attached to. Lots of horror/campfire stories about that kind of stuff. Obviously, it doesn’t happen every day/often, but when/if it does it can be a big deal.
The story that converted me to always using lockers was a raft guide getting thrown during a bit hit- and a non-locking biner on his table clipped through the back of his knee around the tendon.
For myself: In boating I like every biner I play with to be an autolocker (exactly b/c of the stories mentioned above). I used to use standard screw-gate lockers boating, only to look down while moving biners around to discover that one was unlocked- either b/c I forgot to lock it, or because it kept getting jostled in a way that unscrewed it (say on a flip line). It’s now no more effective than a non-locker to me. Simple problem. Simple solution. Now I use autolockers. I’m only carrying a handful of them so weight is a non-issue for me here. Obvious disadvantages- harder to open especially if the mechanism gets filled with sand, weight, cost. If you’re carrying many they don’t rack as well. I recommend making sure you can handle whatever biner you get while wearing gloves too, if you’re going to play in the cold. Make sure it works with your pulleys, etc. Not all of them fit together nicely.
My preference is to have a biner that doesn’t have a “hook” on it where the gate closes, so it’s doesn’t snag on stuff. Some people specifically like one with a hook on it, so if you open it up and it has a bunch of stuff already on it (say climbing nuts), then it’s less likely they’ll all fall off the moment you open it.
There are few biners on the market that are autolockers that don’t have the hook. Petzl has 3 models that meet that spec. BD has 1 that I know of- RockLock Carabiner - Carabiners / Quickdraws - Climbing Carabiners, Quickdraws, Lockers // Black Diamond - Black Diamond Equipment, Ltd.
Kong may have some. I’m not immediately aware of any others, but it’s been years since I’ve looked since I’ve found what works for me.
That being said, I never use autolockers in other sports. Sports-specific preferences. shrug.