We report three-dimensional quantum mechanical calculations on the photodissociation dynamics of CH3I and CD3I on new ab initio potential energy surfaces. The improved potentials are obtained in the contracted spin-orbit configuration interaction framework by using a larger basis set and more spin-free configurations. The dynamical model includes the C-I stretch, C-H-3 umbrella bend, and I-C-H-3 bend and allows the overall rotation. The wave packet is propagated in the Chebyshev order domain. The absorption spectrum, product vibrational and rotational distributions, I* quantum yield, and state-reserved angular distributions are calculated for the parent states of JMK]= \000] and \111], and compared with experiments. The new potential energy surfaces yield a much better agreement with the experimental absorption spectrum, thanks to small potential gradients in the Franck-Condon region. The calculated rovibrational distributions of the methyl fragment are also in good agreement with experimental data. It is shown that the overall rotation has significant effects on the methyl rotational and vibrational distributions as well as the I* yield.