I am using a VM server and not actually physical. Would the DMZ option be better suited for a VM?
All depends on the customer and their IT support... Mitel fully supports Server-Gateway or Server-Only DMZ configuration in a virtual environment (and maybe LAN only, but I have never used this configuration on any MBG)
I prefer to still use Server-Gateway mode if possible, but this requires bringing a public VLAN into the VMWare environment and assign it to a second virtual NIC on the VM.
For example: Voice VLAN 6 is on NIC1 and Public VLAN666 is on NIC2, you setup the static's like a normal physical server. This is the cleanest and easiest from our perspective because we don't have to deal with an external firewall.
Problem with this is some IT support people frown on putting a public VLAN into their Vsphere environment and you have to run it that way for "security" concerns (which there are none if it's properly configured, the MGB firewall is better than anything they might have).