I'll be going in completely blind here, save for knowing about that "This guys whole thing is just one big final dungeon". Could someone give me a spoiler-free breakdown on what each one entails?
i'm considering things explained in the openings not to be spoilers
red - tokusatsu themed story, where the main character becomes a suited-up hero (under certain conditions). the suit has some powered up fist specials you can't otherwise get (he's also the only main character who other characters can't ever recruit, although it seems like fuse will break that rule and some others). it's pretty linear at the start, though it opens up near the end. i'd say the final dungeon and bosses on the harder side overall though
blue - oriented toward the magic-learning sidequests, you pick a few to do and then go off for a magician's duel against the opposite schools. decently guided, mostly not that hard since by the end when you have all the magic you could want your main character is kind of busted (don't overwrite a save if you go into
the kylin's domain though, it's one of the most difficult boss fights in the game and you can't power up or leave as far as i know. in general though, at least on the ps1 version, you should just quicksave any time you're not sure how to return to a hub (usually koorong)...)
asellus - after a long opening, the plot progression mostly occurs abruptly as you wander around for most of the game. i think it's a good balance of freedom and story, and probably lets you reach the highest overall power levels of characters, and the last bosses aren't super hard. has multiple endings, although it seems easiest to get the good one (it's always accessible from the point of no return) and you can kinda switch between them at the end to some degree if you haven't locked yourself out completely. (this may be different in
remaster since apparently they're adding back in some of the events that were originally planned to have affected the ending-in the ps1 version there's just a couple of very binary elements.) i'd say it's on the easier side, but not the easiest.
emelia - a normal human woman looking for her lover's killer. she gets different outfits, which supposedly affect growths (though i don't think it's very noticeable). moderately guided like red's story, though with more freedom earlier on. maybe the easiest final boss. it was definitely my least favorite though, so even though it does a decent job of leading you to things you might want to know on later runs...i have a hard time recommending it first
t260g - a robot who can recruit a full party of other robots, she doesn't remember what she was supposed to be doing. feels like the most linear and traditional jrpg story to me, but that's somewhat subjective. it's great either way, easily my favorite. it's easy to raise the battle rank quickly though, so the ending can be kind of hard.
riki - a monster who's looking for magical "rings" to save his homeland. they have strong effects, but the quest has some very mean parts at the end, and is probably the hardest of all since you also can't get some strong things other characters have. monsters are fun though, and the story is pretty hilarious. i liked it a lot, and finished it first so it's not like it's impossible
lute - a human who can recruit most characters. you can essentially go to the ending right away, or at any time after. good if you're happy wandering around, or know what you want to do-like estragon i played it as a kind of "victory lap" where i recruited a bunch of strong or cool things i wanted to use. the last boss is
hard, though without the same kinds of rude mechanics that riki sees late on.