I believe everyones experience will differ even with the same species.
Aggressive behaviour from any fish can depend on so many factors. Tank size, water flow, temperature and chemistry. Can have affect. As can tank decor, ie territories and hiding spots and line of sight breaks.
Diet can also affect a fishes behavior. Fish can vary on temperament within the same species, due to variant or genetics or possibly individual personality. The list goes on.
We have a general idea of what species tend to act more aggressive on average, but little more than that.
To me the thread is a little pointless. It s probably my least favourite thread on the cichlid forums. Pointless and mute.