These are more different states of the game.
If you try to create City Blocks without some sort of starter base you in for a very slow bad time, simply due to number of bots and resources you need.
Generally, a main bus is used to get to automation of bots and various essential supplies (Electric Poles, Concrete, Rail Tracks, Assemblers etc) then you can start to transition.
If you have biters, you’ll want artillery as city blocks take a huge amount of space and clearing manually would take ages.