Contact coils is hotter as they concentrate the heat and slightly faster ramp-up time. Spaced coils takes a little more wattage for the same heat, but gives imho better flavor.
Imagine lighting e.g. 5 matches at once with space in between; you'll get an even burn/heat over the area, whereas when lighting 5 matches right next to each other, you actually get more heat than before, but in a more narrow/concentrated area... This is why some feel contact coils burns there juice and/or scorches wick, and why spaced coils last longer before rewicking. Also why there's better flavor with spaced coils as the vaporization happens over a wider area of wick, although with less concentrated heat... Lastly, contact coils are often easier to rewick and reuse for longer time...
I personally use contact coils because I love very hot builds/short-draws and vape unflavored anyway...
Personal preference really, which you'll only get by experimentation
