I would have to say,assembly was a waste of Bungie's time....But Sandbox is the best map ever made! There are so many more options to think of than on Foundry or Sand Trap
MOO(My Opinion On):Assembly
My opinion on Assembly is a waste of time,there is nothing you can do with the map unless your trying to build a clever CTF game...Anything other than that....That map is useless...
MOO:Orbital
My opinion on Orbital,is almost the same as my opinion on Assembly...Sorta useless...BUT! There is more room to work with...More open space.
MOO:Sandbox
My opinion on Sandbox is.....It's the greatest map ever created,there are so many things you can edit,down to the way the map is shaped.Even though the skull is pretty difficult to obtain,this map is wonderful.