"You have something that you can take out of the box and have big labels on it that say 'plug this in here,' and you get up and running," he said. Compliance issues, institutional culture and other extenuating circumstances also contribute to the continued need for WAN optimization appliances in a physical form.

On the other hand, as Buccella pointed out, simply making the argument that hardware represents an easier deployment proposition than software is problematic in certain respects -- while physical devices have to be shipped somewhere, purely software-based WAN optimization can just be downloaded and installed on an existing machine or VM.

What's more, the issues of convenience highlighted by Day cut both ways, according to Buccella. Sending a physical appliance to China or India, for example, could be a much bigger hassle than implementing such a system remotely.

Day conceded that "the trend here is very much in favor of the value being in software." However, he added, this fact on its own doesn't mean that hardware is going away.

"There are people that get value out of [physical appliances] and I don't think there's any reason to stop selling them," he said. Moreover, those physical appliances have another key advantage -- what you see is what you get.