If the coils are the same electrical width, then the coil that has more copper in it is more efficient. (also the coil that fits the same copper in a smaller air gap, due to more compact coil configuration.)
The problem with serpentine coils is the end turns are slightly longer. this may not matter depending on other details. for example the 12 pole 36 slot car alternator, due to the length to width ratio of the coils, it probably wouldn't make a significant difference if it was serpentine wound or if each pole had its own coil.
in the first example, you can see that you can't fit any more copper in the coil structure without making the coil less efficient electrically, that is, making the inside width approach zero. which wastes copper losses because a coil with a width of zero doesn't make any voltage. by volume, the first coil might be half as efficient as a solid plate of copper.
in the second example, it appears you can add about 50% more turns and still fit those coils in place. also the end turns are longer than they need to be. you can make the second configuration with separate coils, you are not stuck with the serpentine configuration.