Muon spin rotation (μ + SR) measurements of square-root second moments of local magnetic fields σ in superconducting mixed states, as published for oriented crystals and powder samples of YBa 2 Cu 3 O 7-δ ( 0.05), YBa 2 Cu 4 O 8 and La 2x Sr x CuO 4 (x ~ 0.15-0.17), are subjected to comparative analysis for superconducting gap symmetry. For oriented crystals it is shown that anomalous dependences of σ on temperature T and applied field H, as-measured and extracted a-and b-axial components, are attributable to fluxon depinning and disorder that obscure the intrinsic character of the superconducting penetration depth. Random averages derived from oriented-crystal data differ markedly from corresponding non-oriented powders, owing to weaker influence of pinning in high-quality crystals. Related indicators for pinning perturbations such as non-monotonic H dependence of σ, irreproducible data and strong H dependence of apparent transition temperatures are also evident. Strong intrinsic pinning suppresses thermal anomalies in c-axis components of σ, which reflect nodeless gap symmetries in YBa 2 Cu 3 O 7-δ and YBa 2 Cu 4 O 8 . For YBa 2 Cu 3 O 7-δ , the crystal (a-b components, corrected for depinning) and powder data all reflect a nodeless gap (however, a-b symmetries remain unresolved for crystalline YBa 2 Cu 4 O 8 and La 1.83 Sr 0.17 CuO 4 ). Inconsistencies contained in multiple and noded gap interpretations of crystal data, and observed differences between bulk μ + SR and surface-sensitive measurements are discussed.