Similarly, the three codecs require differing amounts of processing power -- 14 MIPS, 5.5 MIPS and 38 MIPS. So there are trade-offs that vendors have to weigh in making their selections.

And there are trade-offs that customers have to make as well, says Knight. "Except for specific environments where the need is clear, you would put HD voice in the category of a luxury," he says. "But if the choice is between systems that are equivalent in cost, then an HD option is something that's nice to have."