If you hook the vacuum pump directly to the table, you probably will need a big one.
If you hook the vacuum pump to a few stout tanks to act as vacuum storage containers. Then hook the tanks to the table through a valve, you can get by with a smaller pump. It has to work longer to take the whole system down but you can create a HUGE vacuum reserve in the tanks before you call upon it to hold down your work piece.
This opinion is based on a project that I reasearched a few years back that used a Harbor Freight venturi vacuum generator to generate enough vacuum capacity to form plastic. It used two portable compressed air tanks as vacuum storage containers.
For a big one, I would use two or three old water heaters.