In this work we study the main differences between the superconducting properties of the Bi4Sr3Ca3Cu4Ox and (Bi0.8Pb0.2)4Sr3Ca3Cu4Ox glass-ceramics. The Bi 4 Sr 3 Ca 3 Cu 4 O x and (Bi 0.8 Pb 0.2 ) 4 Sr 3 Ca 3 Cu 4 O x glass--ceramics prepared in the same conditions contain similar amounts of the superconducting 2212 phase, however their superconducting and normal--state electrical properties differ significantly. The main reason which makes BiSrCaCuO glass-ceramics worse superconductor than BiPbSrCaCuO is its microstructure.