I have used quite a lot of different AIOs on my bubs and I must say I prefer fitteds with a cover for poo explosions. J&N are doing once a week mega poos and I find that I can get some leakage around the legs with most AIOs. The issue seems to be getting it tight enough around the legs. The best AIO I have used for poo containment is Bubblebubs because I think that has less fabric in the crotch area (and probably doesn't last quite as long).
I find it easier to have the 2 layers of containment that a fitted with cover gives
I absolutely love the AIOs I use (CK HBs, itti bittis, Rosie's Naps, Rumpsters, Bubblebubs) for all of the other wee days though.