It is true for some riders on some bikes that bar ends may be easier to use than down tube shifters, but there are a number of factors that may affect whether that is true for a particular rider. I suspect that when folks say that bar ends are easier it is often because the have to reach down much farther than they do for bar ends. When on a large frame in an upright posture that would very much be the case. That said if on a smaller frame and/or with lower bars it may actually be a more natural reach. See the picture below of one of my bikes set up for ultralight touring. The bar ends would be at pretty much the same height ad the down tube shifters and I actually find it more natural to reach to that shifter position.


That said brifters are much more easy to use, but a bit more expensive, slightly harder to keep adjusted, and maybe a bit less robust. For me it is brifters or sti with bar ends not even in the running. For someone else they may be the winning ticket.