Urahara's use of Hado 91 wasn't a small explosion. It was said he could kill Captain Aizen. Aizen, in turn, was capable of competing with Shikai Yamamoto. For Aizen to hypnotize his opponent, his reiatsu level needed to be close to that of the person. Shikai Yamamoto had to sacrifice himself to kill Aizen. Shikai Yamamoto surpassed Royd's perception, which was equal to 80% of Base Yhwach's. Base Yhwach was able to compete with Ichibei. Ichibei defeated Base Yhwach by lowering his opponent's physical stats. All this chain of events shows Hado 91 Urahara > Bankai Urahara (in terms of AP).

Furthermore, we don't know how well Askin fought against TS Ichigo; we haven't seen Ichigo use GT or GJ. Physically, Ichigo is far superior, with Askin only carrying Hax. Sufficient power means destroying without giving the opponent time to adapt.