GJHorn,
Typically, organizations use both. It's not an "either or" because vBoot does not replace PXE boot provisioning. The only difference is how the target machine receives a copy of WinPE. But it is a critical difference. A machine without a functioning OS needs to PXE boot in order to get provisioned. vBoot only works if the machine has a working OS and a working LD Agent.
The scenarios are:
vBoot = In place provisioning over en existing OS. Ex. Schedule a provisioning task in the console and drag that target machine into your scheduled provisioning task. The machine must be on and already booted into Windows. PXE is bypassed entirely here. However, that is only possible because the original OS and LD Agent downloaded WinPE prior to rebooting. Great for 1 off deployments or classroom refresh deployments.
PXE = Provisioning from a Network boot. Machine can be in any state (No OS, corrupt OS, or functioning OS). The PXE server transfers a copy of WINPE via TFTP to the machine which, in turn, allows the machine to boot into an OS and proceed with the rest of the Prov. Actions. Great for mass deployments and standardized rollouts.
vBoot and PXE provisioning templates are identical except for that 1 action that I included in the screenshot. Other than that, they are identical.
I hope this helps.