Sure all lopp runners are not the same but for all intensive purposes most people do use a sling like you said BUT no matter what a single beener is rated at running or dropping a wieghted rope on such narrow surface is going to F up your rope. If you got stuff that heavy you should step up to a pulley to stop the stress on the rope.
A redirct does not always carry the full load and eager energy is the engery stored in the limbs you manipulate to the ground, its just waiting to be underestimated... eagerly. Ennergy, force, weight, whatever.
It has to be real light for my to just use a beener as a means of lowering. But if two are used to offset the bend of just one its not so bad. Just don't use 3-strand.
i hear ya. I use a biner sometimes by itself on a redirect which isnt supporting the whole load. I didnt list everything I use. the thread was what is your favorite and I enjoy what these two 'tools' achieve for me on a daily basis. sometimes attached to a figure 8 belay. sometimes to a micro pulley. sometimes to a rope snap. The thing that is common here is that there is always the use of a loop runner and a biner in each scenario. When stepping it up to the big stuff. I use a tenex whoopie and an ISC block for 1/2. and even bigger non adjust tenex to a 3/4 block w/ stable braid.