I think some visualizations should help.
Ford Gen 1 Coyote cutaway:
GM LT1 cutaway:
You will see that Coyote has four valves for each cylinder and 2 camshafts above each cylinder bank, while the LT1 has two valves for each cylinder and only 1 camshaft in the valley of the V.
In general, engines are either optimized for high-end or low-end torque/power. An engine that excels at high-end power will have to sacrifice some low-end power and vice versa. The others have already covered the specifics, so in general, Coyote will have better high-end performance due to being able to rev higher, while LT1 is more focused on giving you low-end torque on the go. The LT1 is said to be capable of 300+ lb-ft at 1000 RPM.
This graph should give you an idea of how a pushrod engine(LS7) and a DOHC engine(5.2 Voodoo) delivers the power. Notice that they have similar peak HP figures, but the LS7 gives you more torque down low and that benefits the low-end power.
This is also why the peak HP numbers can be deceiving. In reality, torque curve is a much more important figure to look at and paints a better image of the engine performance.
On another note, because of the low-end torque small blocks are capable of, you don't have to rev them as high when daily driving and they can be geared to rev very slowly on highways, which results in slightly better fuel economy when you compare Camaro SS's EPA test figures to Mustang GT's.
BTW, HP per litre is pretty useless as others have said, especially with this in mind:
If specific output is everything, buy a 2-stroke and Wankel rotary, which make even 4-stroke DOHC engine's specific output look absolutely stupid.