Hi, You'll find loads of info/opinions online about this.
A lof of folk like water knots as they are easy to tie. I find blood knots pretty solid. I often use a knot that I don't even know the name of but it is similar to a figure 8 knot. Dropper rings do seem to be popular but i've never used rings for this purspose so can't comment.
As with so much in fishing people tend to find what works for them and stick with it for a while before moving onto something new, better or just different because they fancy a change. Try some of the more popular knots out there and see what you prefer. Just make sure you tie them as best as you can as its often human error and not the knot type that will let you down!
cheers,
J
