1) GSTR2A is Dynamic statement changing constantly , every day . GSTR2B is Static statement , remain constant no changes .
2) GSTR2A dose not provide any bifurcation GSTR2B provide bifurcation .
3) when supplier file the return of privious period , ITC will reflect in GSTR2A in previous period for i.e If supplier file return for the month of April in July ,ITC will reflect in April GSTR2A . However in case of GSTR2B , when supplier file return for the month of April in July then ITC of April will reflect in the month of July only in GSTR2B .
Only Your purchase details as per books of accounts , reflected in GSTR2B that you have to claim of course you have to fulfill all other conditions too as per CGST act to claim Input tax credit .