the last set of 4" RS branded ones I bought were OK on copper wire but the jaws were too soft for anything else.
If you want to cut piano wire then lindstrom ones are the things to buy. However the jaws are so hard they may be slightly brittle; I have seen the jaws break when the side cutters have been dropped onto a concrete floor, for example.
For general use CK ones are pretty good quality. They are not cheap either though.
BTW I have had some success in resharpening side cutters; it is fiddly work (not least because there are other parts of the mechanism that may prevent the jaws from closing, and these areas will need dressing too) and unless any wear in the pivot can be eliminated, it is a waste of time (you tend to get a 'crossbill' action otherwise).
cheers
