I've used the rubber ball, dog bone, and ladder shaped stops ... and prefer the rubber ball one, but with reservations. They last longer, but are more prone to slipping or hanging in the tip & guides. The dog bone and ladder shaped plastic ones hold their place better, but are harder to get through the tip/guides and harder to change depths with... and they deteriorate (become brittle) faster than the rubber ones. Plus, they kink the line up pretty bad, too

I never got around to using the string ones, but I'd say that if you could cinch them down tight enough & trim them close (and not have to change depths often) ... then they might be a better option, especially if you have a small tip eye & guides.

Many people use dental floss in place of the commercially made strings/bead stops, and just purchase a bag of small plastic beads (with a hole small enough to not allow the knot to pass through). Others, like "ibmack", just use a rubber band and improvise

... cp