Sounds like all you really need is to keep hot foods hot and cold foods cold. If you are cooking in an approved kitchen and they allow you to prepare in one place and then serve in another, I would say go for the smaller of the two units and work into the larger one if need be.
I say that, then think that if you are going to do it why buy small then have to go bigger in a year or so. All depends on your situation.
I am looking forward to "going through" this with you, so keep us posted. Going to be a great thread I think.
KCBS CBJ 9831
Large Spicewine, Backwoods Smoker (Party), WSM, Oklahoma Joe's Offset, Wood Fired Oven