Iterative Soft-Input Soft-Output (SISO) detection and channel decoding offer significant improvement in error-rate performance for a reduced signal-to-noise ratio. With Multiple-Input Multiple-Output (MIMO) technology being part of many wireless system standards, several low-complexity suboptimal detection algorithms have been proposed. In this paper, a detailed flexibility and convergence analysis of Soft-Input Soft-Output List Sphere Decoding and Linear MMSE for MIMO systems is presented. For both techniques, impact of the different system configuration parameters in terms of modulation order and number of antennas is illustrated and discussed. Extrinsic Information Transfer (EXIT) charts are developed in order to thoroughly analyze the behavior and the convergence of the iterative process. This analysis is oriented to obtain possible performance-complexity trade-offs for a flexible hardware implementation.