A crossbody puts the strap over the body, so the bag stays where it is put and both hands stay free -- through a station, a crowd, an evening spent holding something else. A shoulder tote holds several times as much, and it holds it in a shape that stacks: what goes in flat comes out flat. But it hangs from one shoulder and it slides off that shoulder when you lean. So this is a question about the shape of the day rather than about capacity. If anything else has to be carried, the crossbody wins while holding less. If the day is an office and a laptop, the tote is not really being competed with.
Capacity is the easiest thing to compare and the least useful
Litres get printed because they are simple to print, and they say nothing about whether a bag holds a day well. A tote that holds twice as much but has to be set down every time a door is opened is not twice the bag. Compare what the body is doing while it is worn instead, which is the part no specification states.
The second strap is what most people end up wanting
This is why convertible bags exist and why they sell: a tote with a long strap covers most of what a crossbody does, at the cost of some weight. If one bag is going to be bought, a shape that can be worn both ways is usually the honest answer to a choice that is really about the day rather than the bag.