Automated debugging techniques, including fault localization and program repair, have been studied for decades. The existing connection between fault localization and program repair is that fault localization computes the potential buggy elements for program repair to patch. Recently, a pioneering work, ProFL, explored the unified debugging idea to unify fault localization and program repair in the other direction for the first time to boost both areas. More specifically, ProFL utilizes the patch execution results from one state-of-the-art repair system, PraPR, to help improve state-of-the-art fault localization. In this way, ProFL not only improves fault localization for manual repair, but also extends the application scope of automated repair to all possible bugs (not only the small ratio of bugs that can be automatically fixed). In this work, we perform an extensive study of the ProFL unified-debugging approach on 16 state-of-the-art program repair systems for the first time. Our experimental results on the widely studied Defects4J benchmark suite reveal various practical guidelines for unified de-bugging, such as : (1) nearly all the studied 16 repair systems can contribute to unified debugging despite of their varying repairing capabilities, (2) repair systems targeting multi-edit patches canbring noise for unified debugging, (3) repair systems with more executed/plausible patches tend to perform better for unified debugging, (4) unified debugging effectiveness does not rely on the availability of correct patches in automated repair. Based on our study outcome, we further propose an advanced unified debugging technique, UniDebug++, which can localize over 20% more bugs within Top-1 positions than state-of-the-art ProFL.