The most obvious factor as to why VoIP is “better” is cost. If you impliment a VoFR solution, and never consider VoIP as a posibility, you will end up with equipment, configuration, and lines setup for only your voice application. Non-voice data can’t use the paths since there is no routable traffic. It is the common use of the data infrastructure (i.e. IP WAN) that helps to justify the costs when it carries both classes of service. True that there are additional burden’s placed on the MIS folks to get the proper net in place and working, but if used properly, will save money in the mid term.