Which antibody (anti-A or anti-B) usually has the stronger titre?

Anti-A is usually stronger than anti-B.

This once had more significance than it does today, as red cell concentrates stored in newer anticogulant/preservative solutions have less plasma than they once did. For example, the hematocrit (HCT) of red cells stored in CPDA-1 is 0.72 - 0.79 (~200mL red cells in 90 mL plasma). The HCT of red cells stored in CP2D is 0.45 - 0.65: ~200 mL red cells in only 60 mL plasma, with 100 mL AS-3 (Nutricel).

The more plasma in red cell concentrates, the more important it is, in shortages, to select group A red cells as the first choice for group AB patients, when AB red cells are unavailable. This is because group A red cell concentrates will contain anti-B, generally a weaker antibody than the anti-A that group B donors produce.