RCATS for me—especially if there is any problem.
I'm not a fan of the Sonic Tronics glow plug clip as, for some of my models, the push and twist action makes removing the clip a two-handed operation.
However, the connection between the clip and the RCATS cable is a standard RCA audio socket.
I have made up adapters with alligator clips and a spring loaded clip.
When I start using mini banana plugs and remote glow plug leads, I will make up another adapter to suit. It's dead easy to swap connectors as required.