Please pardon me if my question sounds silly, some of the information is pretty new to me. What exactly are the differences between the MCS-I-series (eg MCS-7825-I3) and MCS-H-series (MCS-7825-H3)? One of the seeming differences are that, the I-series supports Cisco Mobile Communicator, while the H-series does not. Are there any other significant differences? Thanks.