On the FF Legends tip (since I think this can function as a shadow early-Kawazu thread), I was trying to remember the difference between mutants and monsters as party members last night, and I ended up try to figure out exactly how their growth systems worked.
My experience as a kid was that I would fill up my FFL1 team with monsters, because–duh–monsters are cool. But also I loved the idea of eating the flesh of my fallen enemies, transforming, and gaining new abilities. It was just so much more exciting than a standard level up. And the monster got 4 unique moves. In retrospect, I have to wonder if pokemon was inspired by FFL’s monsters. But I could never stomach the game for long, because my all monsters party was just too damn random. Like pretty much everyone who played the game, I had no idea what the risk/reward of eating monster meat was, and sometimes I’d have a really cool move, and then–through no real choice other than taking a chance–I’d lose it forever. It was honestly just bewildering and disheartening.
Well, first mutants.
First, while apparently for years people assumed that mutant growth was something like FF2, in which you gained stats based on what you did or what weapons you used, it turns out stat growth was just pseudo-random, as was move changes, albeit with a “you will not ever get weaker moves” clause. Still: you don’t feel like much of a tactician when your party members are morphing every other battle, completely out of your control: http://www.gamefaqs.com/boards/563273-the-final-fantasy-legend/42444042
I guess the perception that mutant growth in FFL had an underlying logic is based on the fact that it did in the FFL2: http://www.shenafu.com/ffl2/mutant.php
Monsters, on the other hand, apparently always had an underlying logic, and it seems to be similar between FFL and FFL2: Each monster species belongs to a genus (slimes and big eyes are both in the “soft” genus), and if a monster from X genus eats meat from Y genus, they become Z genus, with the exact species selected based on the monster’s level. http://www.shenafu.com/ffl2/evolve.php
Basically, you’re assured overall progress, since you’ll gain level and fight more powerful monsters as you progress. But–again–unless you know a fellow eight year old who has mastered spreadsheets and dedicated themselves to eating every randomly dropped piece of monster meat, you’re not going to be able to make informed decisions, which essentially makes monster rearing seem totally random.
Edit: Calling @Aderack to this, just because it seems like his bag.