Greg, you can set the system to only need one transfer switch. When I did the new generator I just added a second panel, instead of trying to rewire everything. Both panels are powered from the single transfer switch, the original panel is just wired into the new panel. This would save you the cost of a second transfer switch.
I would agree. No need for a second transfer switch unless you are planning on paralleling to the utility which most will not allow anyway. Most jurisdictions will also require disconnection from the utility in the event of a utility outage.