I have subcribed to both & FOR ME :
Aquarium Fish was written on a level so that more of the Newbie Hobbyist could follow it w/o too much outside reference to keep up.
I also liked that when they touch on a particular subject, they usually covrred it to my satisfaction & didn't leave me with too many unanswered questions.
TFH,...just seemed to have more Q & A space that appealed to me. FOR ME most of the good stuff that I was the most interested in was in the Q & A section & I would read it, hoping that it would keep continuing on the next page or so & most of the time,...IT DID!
I also liked the ad spots in the back of the book & used them on many occasions to purchase things.
LJx