On my sea kayak I often use carabiners (snap shackles) to attach items to the deck.
The convenience of being able to release the item without tools or too much fumbling is the main reason that a biner is used. Other items, like stays for a sail, that don't require quick release are usually secured by D shackles with a screw on gate.
I use this type of biner for the items that might need occasional use (hand bilge pump secured below deck).
This biner is compact, light and cheap.
But I don't like using this type of gate on a towrope.
There was an incident where the sharp hook ripped somebody's hand open when grabbed by its end.
A larger snap shackle is desirable when trying to attach a towed kayak since some kayak handles will have a hard time accepting a small opening gate.
A larger stainless steel snap shackle from marine chandleries seem to do the job.
What I don't like on this option is the little hook that the biner has when the gate is open and often snags on ropes when least needed.
I thought that a high quality anodized aluminum climbing biner with a key-lock style gate would be the perfect tool.
It was, for a while. The biner has a spring gate and the spring is housed inside the gate itself.
With time the spring corroded and failed leaving the gate wide open. While the rest of the biner still looked in great shape it was no longer usable/safe.
I then tried a carabiner that uses a wire gate as spring. The anodized climbing crab was perfect. The gate was free of hooks that could snag on a rope and would shut securely.
Less then a year later the carabiner started to show signs of corrosion and eventually just exploded!
Finally I sourced a biner that meets my needs.
Stainless steel with a key-hole gate designed for salt water.
The carabiner is made by Kong in Italy (holders of the key-hole gate patent).
There are no signs of corrosion after a year and the action of the gate is very positive.
I don't snag on ropes when releasing from a towline and there are no sharp edges to cut myself on.
The biners come in different sizes but they are not easily sourced. Only high end marine chandleries seem to carry them.