Firemouths or Convicts?

I think - having kept both down the years that there isn't a great deal to choose between them, temperament-wise.

So really it would perhaps be a case of choosing which you prefer.
Firemouths can be a little less aggressive than Convicts, but even this isn't 'hard and fast', especially if not kept in too confined quarters.

One thing, though, to consider is if they breed (and Convicts especially most definitely will, no matter how hard you try to stop them) you would at a guess have a little less difficulty in finding homes for the Firemouth young.

Both are rather insensitive to plants but if you choose less delicate ones like Cryptocorines and Anubias they will fare better than the likes of Cabomba and Vallis would, Anubias - if you can get the plants already growing on bogwood or rocks would be most 'secure' - both Cichlids like to dig and they are no respecters of your plant decor...but if they do get to spawn even these hardy plants aren't safe. They will do their utmost to remove any plant too close to their chosen breeding site. I think this is because a plant would pose a threat by offering cover to would-be egg/fry stealers!

Unless you've already made up your mind between one of these two fish my suggestion would be to look around a little more.
Fish like some of the more hardy Dwarf Cichlids, such as Apistogramma Cacatoides, Borelii too. The Bolivian Rams are quite nice too although some of the imports are really quite bland when compared to the Wild ones. Some Kribs are great - although be warned, the offspring of these can be quite hard to find homes for also. There is another really nice Dwarf Cichlid from Africa which has the common name of 'Butterfly Cichlid' - it used to be linked with what then was called Pelmatachromis (now Pelvichromis) but now is in a different group, the new name beginning with 'A' and it's Thomasi, I really like these too. And all these Dwarf Cichlids have the advantage that your plants will not suffer unduly at their 'hands'.

But, the choice is yours of course, just thought I'd mention a few alternatives just in case.

Let us know what you decide.

Cheers,

John