I have had both, and actually prefer flat benches. In a flat bench, the edges of what would be where the shelves meet, providing a stable place for the pot.
Some things to consider:
Rolling benches. That way you only have one aisle, but by moving the benches, they can be accessed from all sides.
Shelves. Or actually a bench above a bench. High light plants on top, low light plants on bottom. Be sure the upper bench has a way to direct water away from the lower one.
Go vertical. There used to be a grower in a Pittsburgh suburb that had zig-zag rows of 4x4's in the floor, with fencing attached. All pots had little hooks in the edge, and were hung on both sides of the fence. I did the same thing, but made the thing free-standing using sections of galvanized pipe and "kee-klamps" to hold them together.
Space-Saving Plant Rack - First Rays LLC