Irregular moon systems are believed to be one of the most collisionally evolved populations in the Solar System. As such, their size distributions can tell us about recent collisional events. By shifting and stacking CFHT images taken in 2010 and 2019 we performed the deepest search to date on the jovian and saturnian irregular moon systems. The archival jovian search goes to a depth of 25.7 in r band (corresponding to a radius of about 0.4 km) and a depth of 26.5 in w band (or radius of about 1.3km) for the saturnian search. 53 jovian and 122 saturnian candidate moons were detected, of which 7 jovian and 38 saturnians have been linked to already-known moons. From our detections and a careful detection efficiency analysis of our data, we produce debiased size distributions for both saturnian irregular and retrograde jovian irregulars. We find the saturnian size distribution to be steeper than for jovians over the same size range. This points to a likely recent major collision in the retrograde saturnian irregular population.