People are gonna tell you all kinds of nonsense back and forth, Honestly, After using a LOT of coals, the coals do the same thing, coconaras are just over priced but work well, their have been problems with the coals smoking during lighting on a few of the coals or a few coals stuck together etc. Not sure if the quality control or batches were just bad and something went wrong during the manufacture process but CH Nats work well. Same shape coal, only difference is, johns coals I would light in a vented area, just due to they put off a little smell while being lit but to me it doesn't bother me, they both work well, they do their purpose, if they are cheaper I would go for the price efficient coals. As for me, I am looking for other coals over both of them. Just because I miss the old roung finger coals and wood charcoal which gave me good smoke, if your smoking outside and don't mind ash, I smoke wood coals from time to time to bring it back to the og times 8p
All in all whatever coals you get you'll be happy rather it coco or CH.
You will hear opinions and more opinions but being straight forward, they do the same thing, heat up shisha, so you can smoke your bowl, one may have a little more ash then the other, if you want as well even try http://www.shishaco.net/index.html
They all work, whichever has a better price, give them a shot