go with the 105s.

i have a set of ancient ultegras that have the same narrow-body/plastic scuff plate design, and the plates wear out, especially in inclement weather. the result is first squeaky, then sloppy, then unrideable. the r540s appear to still use this design. perhaps materials have improved?

in any case, i also have a couple sets of the newer wide-body/metal scuff design (one ultegra and one DA) and they are far superior. well into five figure mileage on at least one set, zero issues.