In my opinion if you are talking about putting more than 40 amps of continuous load on a site lighting circuit @ 208 volts and you want to keep voltage drop within reason the wire size will get out of control.
Of course this will largely depend on distance.
IMO, running more circuits with less load will be more efficient cost wise.
Say you end up needing 2 AWG for your circuits, now you end up with raceways that will not fit in the poles so you need hand holes in the ground beside the poles. Then the time and matrial for splicing the larger conductors.
By using more circuits if there is a fault you do not darken the entire parking lot.
I would look into kicking the voltage up to 480 for the site lighting, voltage drop and circuit loading problems are greatly reduced.