You have more room when you have just a huge bowl without the divider.
I rinse off small items with water/brush. Those go straight into the dishwasher. One bowl provides more room to wash pots/pans/big stuff/stuff that can't go in the dishwasher, and I use one of those scrub brushes that you put dish soap in the handle of and soap comes out when you press the button (if you have one of those brushes, it kind of eliminates the need to fill one side of the sink with suds as well).
I agree with
@VolNExile that if you hand wash everything, you need a bowl filled with water/soap, so one large sink probably doesn't make sense.