Sharing 3x ISP (SDWAN) among multiple internal VDOMs

[abisgroup]

I have three ISPs (2x Comcast and ATT fiber) that I would like to share between mutliple internal VDOMs (corresponding to internal VLANs). Some of the VDOMs will route primarely over ATT, others might only use 2x Comcasts.  Each ISP has public static IP pools that used to NAT egress traffic. 

I know 5.6.3 introduced a virtual switch that allow to share a physical interface.

So far, I am considering the following two approaches:

1- a dedicated VDOM that handles 3 x ISP with SD-WAN and inter-vdom links connecting to the internal VDOMs. 

2- a virtual switch where the internal VDOMs share physical interfaces connected to indivisdual ISPs.

What are the pros and cons for #1 and #2 architectual designs.

Thanks

OB

[abisgroup]

I was attending FortiGate training yesterday, and I've discussed this issue with a Tech from Chicago. His recommendation is to go with a dedicated VDOM with SDWAN and establish inter-VDOM links to allow other VDOM to get out.