Compressed/contact coils concentrate the heat for quicker warm up times, and potentially more vapor/TH. I say potentially because you still need to consider wicking, if you have too much heat in one area your wick dries out and vapor isn't going to increase. The wick inside the center of the coil will dry out before the wick tails will, so juicy wick tails isn't a sure sign of a well-wicking setup.
They are also easier to work with usually because they keep their shape better than a spaced coil, plus they look professional
Personally I use spaced coils in my kayfuns now but still use compressed in drippers. I've dropped down to about .6 for my kayfuns and compressed coils were severely overheating the juice producing off flavors, once I spaced them flavor was excellent. Drippers have enough airflow so that isn't an issue.
All this stuff is tricky because there are few hard rules, most are conditional because there are so many variables to take into account. Pretty much everything in
vaping is like "xx will increase vapor, if conditions y and z are met" Then the conditions of y and z depend on r and s, and so on. Gets complicated in a hurry
