I have strong webbing tapes secured to strong points on both side decks. My lifejacket has an integral harness, and I use a safety line to clip onto the webbing line when leaving the safety of the cockpit in boisterous conditions and moving forwards. The clip on the lifeline slides along smoothly, and doesn't restrict my movement.
I have a diesel engine, use autopilot a lot, and have no kill cord.
If I was out solo with this arrangement, there is a risk I'd be dragged along until something (or someone) stopped the boat, but I'd still be attached to the boat.
If I was with crew, I'd be spotted as missing, and I'd be attached to the vessel for the first stage of MOB recovery.
I consider it safer than watching the vessel disappear without me.