High quality of service (QoS) for simultaneous speech and data calls is an operational requirement in GSM/(E)GPRS systems. Efficient sharing of resources between voice and data calls, based on movable boundary handover least loaded (MBH LL) is a promising algorithm. Following the ideal case analysis (see Ajib, W., "Gestion de transmission d'un flux temporaire de donne´es dans un re´seau radio mobile d'acce`s TDMA", January thesis report, ENST, 2001), this paper introduces a more realistic evaluation taking into account MS constraints and different MAC options in the GPRS air interface. The results of two MBH LL variants are presented in terms of voice blocking, data GoS (grade of service), and average throughput per call. Simulations show that the MS hardware limitations have little affect on performance in unidirectional data transmission. The same is true for a carefully designed variant of MBH LL for bidirectional operation with multi-slot allocation. Additionally, an enhancement of the algorithm for cell capacity improvement for data calls and a method based on throughput differentiation for data QoS implementation on the radio resource management (RRM) layer are proposed.