a usb phone is basically the same as a headset and microphone except for the fact that it’s a little more comfortable to wear. The USB phones are about as good as you want to pay for them, most are just a speaker and a mic in a cheap cell phone case with a USB interface. I have seen them get as cheap as 13 USD each when bought in qty of 1000 or so. These phones also typically require the use of softphone software on your PC anyways.
Not much advantage in my opinion.