Neither is ideal if you actually want to see behind you without looking over your shoulder. I like the aesthetic of the under bar mirror. It is not very functional. I like to split lanes though and I don’t have to worry about my mirrors hitting a car mirror with this setup. Bar end mirrors may have slightly more visibility depending on the size of the mirror. They do stick out more though, even the folding ones. Either setup is less safe than the stock setup because you have take your eyes off the road to look down at the mirrors for longer. As you can see, I don’t even have a right side mirror so I am shoulder checking every time I change lanes. This mirror is mostly cosmetic and to satisfy The Law. I sometimes use it on the freeway but never in the city.