Verify WPS. Many times I encouter in the projects it already stated in WPS can be done by gouging or by grinding depending on the thickness and diameter to be repair. The weld repair is same as the original welding done as per WPS requirements

Professor Crisi, when one of our 230 mm thick groove welds fail UT at 75-100 MM down, your preference of using grinding disks would change! :)  (not talking pipe here)

Having done more than my fair share of repairs (a couple of jobs I have held, I somehow got designated "repair wizard" and performed virtually all the repairs in the shop) its my opinion that both grinding and ACA have their areas of application. If the repair is likely to be shallow and be a substantial discontinuity, like a short crack, grinding is fine. If the discontinuity is small, like very fine porosity grinding may obscure and hide defects. Aside from the depth issue, ACA gouging is much superior, in the hands of a skilled operator, at finding and positively identifying fine discontinuities.